Storage

August 10, 2026 · View on GitHub

LibreDB Studio uses a pluggable storage abstraction layer that lets it operate in two modes:

Local mode (default): Zero-config, all data lives in the browser's localStorage. Ideal for single-user / open-source usage.
Server mode: Data is persisted to a server-side database (SQLite or PostgreSQL) with per-user scoping. Ideal for teams and enterprise deployments.

Switching between modes requires only one environment variable — no code changes, no rebuild.

This document is split into two parts. Most readers want Part 1 — Setup & Configuration. For internals, see Part 2 — Architecture & Internals.

Part 1 — Setup & Configuration

Which Mode Should I Use?
1. Local Mode (Default)
2. SQLite Mode
3. PostgreSQL Mode
Migration: Local to Server
Credential Encryption at Rest
Environment Variables Reference
Health Check
Troubleshooting
Database Schema Reference

Part 2 — Architecture & Internals

1. Design Goals
2. Architecture Overview
3. Data Model
4. Module Structure
5. Local Storage Layer
6. Storage Facade
7. Server Storage Providers
8. API Routes
9. Write-Through Cache & Sync Hook
10. Migration Flow
11. Configuration
12. User Scoping & Security
13. Docker Deployment
14. Adding a New Provider

Part 1 — Setup & Configuration

LibreDB Studio supports three storage modes. Pick the one that fits your use case and follow the steps below.

Which Mode Should I Use?

Mode	Best For	Persistence	Multi-User	Setup
Local (default)	Solo dev, quick start	Browser only	No	Zero config
SQLite	Small teams, single server	Server file	Yes	1 env var
PostgreSQL	Enterprise, multi-node	External DB	Yes	2 env vars

1. Local Mode (Default)

No configuration needed. All data stays in the browser's localStorage.

# Just start the app — that's it
bun dev

What you get:

Instant start, no database required
Data persists across page reloads
Data is lost if browser storage is cleared or you switch browsers/devices

When to move on: When you need data to survive across devices, browsers, or team members.

2. SQLite Mode

A single file on the server. Great for self-hosted single-node deployments.

Minimal Setup (Just One Env Var)

# .env.local
STORAGE_PROVIDER=sqlite

bun dev

That's it. When STORAGE_SQLITE_PATH is not provided, the default path is ./data/libredb-storage.db.

What Happens Automatically

On the first API request, the SQLite provider:

Creates the directory — ./data/ (or whatever parent directory the path points to) is created recursively if it doesn't exist
Creates the database file — libredb-storage.db is created by better-sqlite3
Enables WAL mode — Write-Ahead Logging for better concurrent read performance
Creates the table — user_storage table with the schema below

No manual setup, no migrations, no SQL scripts needed.

Custom Path

If you want the database file in a different location:

# .env.local
STORAGE_PROVIDER=sqlite
STORAGE_SQLITE_PATH=/var/lib/libredb/storage.db

The directory must be writable by the app process. The directory and file are created automatically.

Docker

# docker-compose.yml
services:
  app:
    image: ghcr.io/libredb/libredb-studio:latest
    ports:
      - "3000:3000"
    environment:
      - STORAGE_PROVIDER=sqlite
      - STORAGE_SQLITE_PATH=/app/data/libredb-storage.db
    volumes:
      - storage-data:/app/data

volumes:
  storage-data:

docker-compose up -d

Volume is essential. Without it, data is lost when the container restarts.

Verify

curl http://localhost:3000/api/storage/config
# → {"provider":"sqlite","serverMode":true}

Manual Table Creation (Optional)

The table is auto-created, but if you prefer to create it yourself (e.g., for auditing or version control):

CREATE TABLE IF NOT EXISTS user_storage (
  user_id    TEXT NOT NULL,
  collection TEXT NOT NULL,
  data       TEXT NOT NULL,
  updated_at TEXT NOT NULL DEFAULT (datetime('now')),
  PRIMARY KEY (user_id, collection)
);

-- Recommended: enable WAL mode for concurrent read performance
PRAGMA journal_mode = WAL;

3. PostgreSQL Mode

Recommended for production, teams, and high-availability deployments.

Important: Unlike SQLite, STORAGE_POSTGRES_URL is required. There is no default value. If you set STORAGE_PROVIDER=postgres without providing a connection string, the app will throw an error on the first storage request:
Error: STORAGE_POSTGRES_URL is required when STORAGE_PROVIDER=postgres

Local Development

# Start a PostgreSQL instance (if you don't have one)
docker run -d --name libredb-pg \
  -e POSTGRES_DB=libredb \
  -e POSTGRES_USER=libredb \
  -e POSTGRES_PASSWORD=secret \
  -p 5432:5432 \
  postgres:16-alpine

# .env.local
STORAGE_PROVIDER=postgres
STORAGE_POSTGRES_URL=postgresql://libredb:secret@localhost:5432/libredb?sslmode=disable

bun dev

What Happens Automatically

On the first API request, the PostgreSQL provider:

Creates a connection pool — max 5 connections, 30s idle timeout
Handles idle-client failures — the pool gets an error listener immediately (see below)
Creates the table — user_storage table with the schema below via CREATE TABLE IF NOT EXISTS

The database itself must already exist. The table is auto-created, but the database is not.

This pool is long-lived: once created it serves every storage request for the life of the process. A pooled client that fails while idle — the server dropped it, the network went away, the DBA restarted the database — has no query to reject, so pg destroys it and emits error on the pool. Node treats an error event with no listener as an uncaught exception, so the provider attaches one that logs through the storage logger (provider=postgres) and lets the pool open a fresh client on the next request. A dropped idle connection therefore costs one log line, never the server process. The PostgreSQL database provider carries the same guard for the same reason (see providers/postgres.md).

Required Privileges

The PostgreSQL user specified in STORAGE_POSTGRES_URL needs:

Privilege	Why
`CREATE TABLE`	Auto-create `user_storage` on first request (only needed once)
`INSERT`	Save user data
`UPDATE`	Update existing data
`SELECT`	Read user data

If your DBA restricts CREATE TABLE, you can create the table manually (see below) and the user only needs INSERT/UPDATE/SELECT.

Docker Compose (App + PostgreSQL)

# docker-compose.yml
services:
  app:
    image: ghcr.io/libredb/libredb-studio:latest
    ports:
      - "3000:3000"
    environment:
      - STORAGE_PROVIDER=postgres
      - STORAGE_POSTGRES_URL=postgresql://libredb:secret@db:5432/libredb?sslmode=disable
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:18
    environment:
      - POSTGRES_DB=libredb
      - POSTGRES_USER=libredb
      - POSTGRES_PASSWORD=secret
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U libredb"]
      interval: 5s
      timeout: 3s
      retries: 5

volumes:
  pgdata:

docker-compose up -d

Using an Existing PostgreSQL

Just set the connection string — the table is auto-created:

STORAGE_PROVIDER=postgres
STORAGE_POSTGRES_URL=postgresql://user:pass@your-pg-host:5432/your_db

Use sslmode=disable for local/non-SSL PostgreSQL and sslmode=require for managed cloud PostgreSQL:

# Local PostgreSQL
STORAGE_POSTGRES_URL=postgresql://user:pass@localhost:5432/your_db?sslmode=disable

# Cloud PostgreSQL
STORAGE_POSTGRES_URL=postgresql://user:pass@your-pg-host:5432/your_db?sslmode=require

Verify

curl http://localhost:3000/api/storage/config
# → {"provider":"postgres","serverMode":true}

Manual Table Creation (Optional)

The table is auto-created on first request. However, if you prefer to create it yourself — for example, in environments where the app user doesn't have CREATE TABLE privileges, or you want to track schema changes in version control:

-- PostgreSQL
CREATE TABLE IF NOT EXISTS user_storage (
  user_id    TEXT NOT NULL,
  collection TEXT NOT NULL,
  data       TEXT NOT NULL,
  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  PRIMARY KEY (user_id, collection)
);

-- Optional: index for faster lookups by user
CREATE INDEX IF NOT EXISTS idx_user_storage_user_id ON user_storage (user_id);

Minimal Privileges (When Table Already Exists)

If a DBA creates the table, the app user only needs:

-- Grant only data access (no DDL needed)
GRANT SELECT, INSERT, UPDATE ON user_storage TO libredb_app;

Migration: Local to Server

When you switch from local mode to SQLite or PostgreSQL, existing browser data is automatically migrated on first login:

User opens the app in server mode
The sync hook detects it's the first time (no libredb_server_migrated flag)
All existing localStorage data is sent to the server via POST /api/storage/migrate (a fresh browser with no libredb_* data simply sets the flag and skips the upload)
Server upserts each collection as a whole JSON blob — one row per user per collection, replacing any existing row
A flag is set in localStorage to prevent re-migration
From this point on, the server is the source of truth

No manual steps required. Just change the env var and restart.

If multiple users were sharing a browser in local mode, only the data from the user who migrates first will be sent. Each user's server storage is isolated by their login email.

For the full migration lifecycle and the underlying merge semantics, see Migration Flow in Part 2.

Credential Encryption at Rest

In sqlite and postgres modes, credentials are encrypted before they are written. There is nothing to switch on and nothing to configure.

What is encrypted

Seven fields, all on a saved connection:

Field	What it is
`password`	The database password
`connectionString`	A URL that can embed `user:password@`
`agentPassword`	The optional least-privilege agent-profile password (#328)
`ssl.clientKey`	The TLS client private key
`sshTunnel.password`	The SSH password
`sshTunnel.privateKey`	The SSH private key
`sshTunnel.passphrase`	The passphrase that unlocks the key above

Everything else stays readable, deliberately: host, port, user, agentUser, database, name and the TLS certificates (ssl.caCert, ssl.clientCert — certificates are public by construction). An operator holding a dump has to be able to answer "which of my databases is in here"; that is incident response, not a leak. No other collection is touched — history and saved_queries hold SQL text, which is the product's data rather than its secrets.

Each value is stored as v1:<iv>:<ciphertext> using AES-256-GCM with a fresh random IV, so two identical passwords do not look identical in the store, and a tampered value is detected rather than silently decrypting to something else.

The key

`STORAGE_ENCRYPTION_KEY`	Key used
unset (default)	Derived from `JWT_SECRET` via HKDF-SHA256
set (min 32 characters)	Derived from that value via HKDF-SHA256

Deriving from JWT_SECRET is what keeps the zero-config promise: no new required variable, and if you never set JWT_SECRET either, the first-run bootstrap generates and persists one (<data dir>/auth-bootstrap.json), so the key is stable across restarts.

Set a dedicated STORAGE_ENCRYPTION_KEY where key separation matters — most usefully so that rotating your session-signing secret does not also invalidate every saved connection password.

Rotating a key invalidates stored credentials

This is the trade-off, stated plainly: rotating whichever key is in use makes every stored credential unreadable. That applies to rotating JWT_SECRET when STORAGE_ENCRYPTION_KEY is unset, and to rotating STORAGE_ENCRYPTION_KEY when it is set. It also applies if you lose the bootstrap file — a container without a persistent volume for its data directory regenerates JWT_SECRET on every start.

What happens is bounded and recoverable:

The connection survives. Its name, host, port, user and database are still there.
The unreadable field is omitted, not replaced with garbage. The password box is empty.
A warning is written to the server log once per read: Stored connection secrets could not be decrypted: N field(s) were omitted.
Nothing is deleted from the database by the read itself.

To recover, restore the previous key and restart, before using the app. Reads happen on page load; the first time the app writes that collection back, the omitted values are gone for good, because the browser copy is the source the server is updated from. If you cannot restore the key, re-enter the affected passwords once and they are re-encrypted under the current key.

Existing deployments migrate themselves

Reads accept both plaintext and encrypted values, and writes always produce encrypted ones. An existing store therefore migrates as it is used, with no migration command, no downtime and no version column. A row that is never written again stays plaintext — which is why the STORAGE_ENCRYPTION_KEY upgrade is safe to roll back.

What this does not protect

Browser localStorage is not encrypted. It is the rendering source and it holds the same credentials in the clear. That is a deliberate product decision — it is what lets Studio work without a master password — and it is why cross-site scripting is treated as a top-severity issue in this project rather than a session-theft issue.
Anyone who can read the server's environment can read the credentials. The key lives there. This protects a stolen database file or dump on its own; it is not a vault.
For STORAGE_PROVIDER=sqlite with no STORAGE_ENCRYPTION_KEY set, a backup or volume snapshot is NOT protected. The fallback key derives from JWT_SECRET, persisted in <data dir>/auth-bootstrap.json — the same directory STORAGE_SQLITE_PATH puts the database file in, and the one directory the Helm chart mounts as a single /app/data volume. A snapshot of that volume carries the ciphertext and the key that opens it side by side. Set STORAGE_ENCRYPTION_KEY from outside that volume — a Kubernetes Secret, an environment variable your orchestrator supplies — to close this: once the key is not itself part of the backup, a snapshot is genuinely useless without it. STORAGE_PROVIDER=postgres does not share this exposure by default, because the key material lives in the app's own filesystem, a volume separate from the database that gets backed up.
GET /api/storage returns credentials in plaintext to their authenticated owner. It has to: the app must be able to redisplay a saved password for editing.

Environment Variables Reference

Variable	Required	Default	Description
`STORAGE_PROVIDER`	No	`local`	`local`, `sqlite`, or `postgres`
`STORAGE_SQLITE_PATH`	No	`./data/libredb-storage.db`	Path to SQLite file. Directory and file are auto-created.
`STORAGE_POSTGRES_URL`	Yes (postgres mode)	—	PostgreSQL connection string. No default — app will error without it.

These are server-side only variables (no NEXT_PUBLIC_ prefix). The client discovers the mode at runtime via GET /api/storage/config. This means one Docker image works for all modes. See Why Not NEXT_PUBLIC_*? for the rationale.

Default Behavior Summary

Mode	Config needed	What's auto-created
`local`	Nothing	N/A (browser localStorage)
`sqlite`	Just `STORAGE_PROVIDER=sqlite`	Directory + DB file + WAL mode + table
`postgres`	`STORAGE_PROVIDER=postgres` + `STORAGE_POSTGRES_URL`	Table only (database must exist)

Health Check

Check if the storage backend is reachable:

# Storage mode info (always works, no auth needed)
curl http://localhost:3000/api/storage/config

# Full data fetch (requires auth cookie)
curl -b cookies.txt http://localhost:3000/api/storage

Troubleshooting

"Data not syncing to server"

Check storage mode: curl http://localhost:3000/api/storage/config
Make sure the response shows "serverMode": true
Check browser console for sync errors (look for [StorageSync] prefixed logs)

SQLite: "SQLITE_CANTOPEN"

The directory in STORAGE_SQLITE_PATH must be writable by the app process
In Docker, make sure the volume is mounted correctly

PostgreSQL: "STORAGE_POSTGRES_URL is required"

You set STORAGE_PROVIDER=postgres but didn't provide STORAGE_POSTGRES_URL
Unlike SQLite, PostgreSQL has no default — a connection string is always required
Fix: add STORAGE_POSTGRES_URL=postgresql://user:pass@host:5432/dbname to your env

PostgreSQL: "Connection refused"

Verify STORAGE_POSTGRES_URL is correct and the database is reachable
In Docker Compose, use the service name (db) as the host, not localhost
Check that the PostgreSQL container is healthy: docker-compose ps

PostgreSQL: "server does not support SSL connections"

Your PostgreSQL server does not accept SSL, but SSL is enabled in the connection URL
Fix local setups by adding ?sslmode=disable to STORAGE_POSTGRES_URL
For managed cloud PostgreSQL, use ?sslmode=require

"Data disappeared after switching modes"

Switching from server mode back to local mode doesn't pull data from the server
Local mode only reads from localStorage
To recover: switch back to server mode, the data is still in the database

"My connection passwords are blank after a restart"

Look for this line in the server log:

Stored connection secrets could not be decrypted: 3 field(s) were omitted.

The encryption key changed. Either JWT_SECRET was rotated (and STORAGE_ENCRYPTION_KEY is not set), or STORAGE_ENCRYPTION_KEY itself changed, or the data directory holding auth-bootstrap.json was not persisted so a fresh JWT_SECRET was generated on start.

Restore the previous key and restart before using the app — see Rotating a key invalidates stored credentials. If the key is gone, re-enter the affected passwords; everything else about the connection is intact.

"Duplicate data after migration"

Migration runs once per browser (guarded by the libredb_server_migrated flag) and replaces each collection wholesale, so duplicates shouldn't occur
If you do see them, check whether the same user pushed data from multiple browsers before the first migration completed

Database Schema Reference

Both SQLite and PostgreSQL use the same single-table design. The table is auto-created on first request, but the full DDL is provided here for reference.

SQLite

CREATE TABLE IF NOT EXISTS user_storage (
  user_id    TEXT NOT NULL,
  collection TEXT NOT NULL,
  data       TEXT NOT NULL,
  updated_at TEXT NOT NULL DEFAULT (datetime('now')),
  PRIMARY KEY (user_id, collection)
);

PRAGMA journal_mode = WAL;

PostgreSQL

CREATE TABLE IF NOT EXISTS user_storage (
  user_id    TEXT NOT NULL,
  collection TEXT NOT NULL,
  data       TEXT NOT NULL,
  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
  PRIMARY KEY (user_id, collection)
);

-- Optional: index for faster lookups by user
CREATE INDEX IF NOT EXISTS idx_user_storage_user_id ON user_storage (user_id);

Schema Explanation

Column	Type	Description
`user_id`	TEXT	User's email from JWT token (e.g., `admin@libredb.org`)
`collection`	TEXT	Data category: `connections`, `history`, `saved_queries`, `schema_snapshots`, `saved_charts`, `active_connection_id`, `audit_log`, `masking_config`, `threshold_config`, `dismissed_seeds`
`data`	TEXT	JSON-serialized collection data
`updated_at`	TEXT / TIMESTAMPTZ	Last modification timestamp

Each row stores one user's one collection as a JSON blob. Adding a new collection type requires no schema changes — just a new row.

Part 2 — Architecture & Internals

This part describes the internals of the storage abstraction layer: design goals, module structure, the storage facade API, provider interface, the write-through cache, the useStorageSync hook lifecycle, migration flows, and the security model.

1. Design Goals

Goal	Approach
Zero breaking changes	All 16+ consumer components keep the same synchronous `storage.*` API
Zero-config default	`localStorage` works out of the box — no database, no env vars needed
Single image, all modes	Runtime config via env var, not build-time `NEXT_PUBLIC_*`
Per-user isolation	Server storage scoped by JWT `username` — no cross-user leaks
Graceful degradation	If server is unreachable, `localStorage` continues to work
Extensible	Adding a new backend (e.g., MySQL, DynamoDB) requires one file implementing `ServerStorageProvider`

2. Architecture Overview

┌──────────────────────────────┐
│   16+ Consumer Components    │  ← Unchanged, same sync API
│   storage.getConnections()   │
│   storage.saveConnection()   │
└──────────────┬───────────────┘
               │ sync read/write
┌──────────────▼───────────────┐
│   Storage Facade             │  ← localStorage read/write + CustomEvent dispatch
│   src/lib/storage/           │
│   storage-facade.ts          │
└──────────────┬───────────────┘
               │ CustomEvent: 'libredb-storage-change'
┌──────────────▼───────────────┐
│   useStorageSync Hook        │  ← Mounted in Studio.tsx (server mode only)
│   src/hooks/                 │
│   use-storage-sync.ts        │
└──────────────┬───────────────┘
               │ fetch (debounced 500ms)
┌──────────────▼───────────────┐
│   API Routes                 │  ← JWT auth + user scoping
│   /api/storage/*             │
└──────────────┬───────────────┘
               │
┌──────────────▼───────────────┐
│   ServerStorageProvider       │  ← Strategy Pattern
│   ┌─────────┐ ┌────────────┐ │
│   │ SQLite  │ │ PostgreSQL │ │
│   └─────────┘ └────────────┘ │
└──────────────────────────────┘

Key insight: localStorage is always the rendering source (L1 cache). The server database is the persistent source of truth (L2). The sync hook keeps them in sync via a write-through cache pattern.

3. Data Model

3.1 Collections

All application state is organized into 10 collections, each stored as a JSON blob:

Collection	Type	Description	Max Items
`connections`	`DatabaseConnection[]`	Saved database connections	—
`history`	`QueryHistoryItem[]`	Query execution history	500
`saved_queries`	`SavedQuery[]`	User-saved SQL/JSON queries	—
`schema_snapshots`	`SchemaSnapshot[]`	Schema diff snapshots	50
`saved_charts`	`SavedChartConfig[]`	Saved chart configurations	—
`active_connection_id`	`string \| null`	Currently active connection	—
`audit_log`	`AuditEvent[]`	Audit trail events	1000
`masking_config`	`MaskingConfig`	Data masking rules and RBAC	—
`threshold_config`	`ThresholdConfig[]`	Monitoring alert thresholds	—
`dismissed_seeds`	`string[]`	Seed IDs the user dismissed (deleted a `managed: false` seed copy) so it is not re-added	—

3.2 Server Database Schema

Both SQLite and PostgreSQL use the same logical schema — a single table with collection-based JSON blobs:

CREATE TABLE IF NOT EXISTS user_storage (
  user_id    TEXT        NOT NULL,          -- JWT username (email)
  collection TEXT        NOT NULL,          -- 'connections', 'history', etc.
  data       TEXT        NOT NULL,          -- JSON serialized
  updated_at TEXT/TIMESTAMPTZ NOT NULL,     -- Last modification time
  PRIMARY KEY (user_id, collection)
);

This design is intentionally simple:

No schema migrations needed when adding new collections
One row per user per collection — efficient upsert
JSON blobs keep the server storage schema-agnostic

The full per-dialect DDL (with defaults and the recommended index) is in Database Schema Reference in Part 1.

3.3 localStorage Keys

Each collection maps to a libredb_-prefixed localStorage key:

connections       → libredb_connections
history           → libredb_history
saved_queries     → libredb_saved_queries
schema_snapshots  → libredb_schema_snapshots
saved_charts      → libredb_saved_charts
active_connection_id → libredb_active_connection_id
audit_log         → libredb_audit_log
masking_config    → libredb_masking_config
threshold_config  → libredb_threshold_config
dismissed_seeds   → libredb_dismissed_seeds

4. Module Structure

src/lib/storage/
├── index.ts              # Barrel export — preserves @/lib/storage import path
├── types.ts              # StorageData, StorageCollection, ServerStorageProvider
├── local-storage.ts      # Pure localStorage CRUD (SSR-safe)
├── storage-facade.ts     # Public storage object with domain methods
├── factory.ts            # Env-based provider instantiation (singleton)
└── providers/
    ├── sqlite.ts         # better-sqlite3 implementation
    └── postgres.ts       # pg (Pool) implementation

src/hooks/
└── use-storage-sync.ts   # Write-through cache hook

src/app/api/storage/
├── config/route.ts       # GET: storage mode discovery (public)
├── route.ts              # GET: fetch all user data (auth required)
├── [collection]/route.ts # PUT: update single collection (auth required)
└── migrate/route.ts      # POST: localStorage → server migration (auth required)

5. Local Storage Layer

File: src/lib/storage/local-storage.ts

Pure, side-effect-free localStorage CRUD with SSR safety:

// All operations check isClient() before accessing localStorage
export function readJSON<T>(collection: string): T | null;
export function writeJSON(collection: string, data: unknown): boolean;  // false on failure (e.g. QuotaExceededError)
export function readString(collection: string): string | null;
export function writeString(collection: string, value: string): boolean; // false on failure
export function remove(collection: string): void;
export function getKey(collection: string): string;  // → 'libredb_' + collection

Every function is guarded by isClient() — safe to call during SSR (returns null / no-op)
JSON parse failures return null instead of throwing

6. Storage Facade

File: src/lib/storage/storage-facade.ts

The public storage object provides the same synchronous API that all 16+ consumer components use. Every mutation method:

Writes to localStorage (immediate)
Dispatches a CustomEvent('libredb-storage-change') with the collection name and data

// Example: saving a connection
storage.saveConnection(conn);
// 1. Reads existing connections from localStorage
// 2. Upserts by ID
// 3. Writes back to localStorage
// 4. Dispatches CustomEvent({ collection: 'connections', data: updatedList })

Public API

Category	Methods
Connections	`getConnections()`, `saveConnection(conn)`, `deleteConnection(id)`, `getDismissedSeeds()`
History	`getHistory()`, `addToHistory(item)`, `clearHistory()`
Saved Queries	`getSavedQueries()`, `saveQuery(query)`, `deleteSavedQuery(id)`
Schema Snapshots	`getSchemaSnapshots(connId?)`, `saveSchemaSnapshot(snap)`, `deleteSchemaSnapshot(id)`
Charts	`getSavedCharts()`, `saveChart(chart)`, `deleteChart(id)`
Active Connection	`getActiveConnectionId()`, `setActiveConnectionId(id)`
Audit Log	`getAuditLog()`, `saveAuditLog(events)`
Masking Config	`getMaskingConfig()`, `saveMaskingConfig(config)`
Threshold Config	`getThresholdConfig()`, `saveThresholdConfig(thresholds)`

All read methods are synchronous — they read from localStorage only. No network calls.

7. Server Storage Providers

7.1 Provider Interface

File: src/lib/storage/types.ts

interface ServerStorageProvider {
  initialize(): Promise<void>;
  getAllData(userId: string): Promise<Partial<StorageData>>;
  getCollection<K extends StorageCollection>(
    userId: string, collection: K
  ): Promise<StorageData[K] | null>;
  setCollection<K extends StorageCollection>(
    userId: string, collection: K, data: StorageData[K]
  ): Promise<void>;
  mergeData(userId: string, data: Partial<StorageData>): Promise<void>;
  isHealthy(): Promise<boolean>;
  close(): Promise<void>;
}

7.2 SQLite Provider

File: src/lib/storage/providers/sqlite.ts Package: better-sqlite3 (Node.js compatible, not bun:sqlite)

Feature	Detail
WAL mode	Enabled for concurrent read performance
Auto-create	Directory and database file created on `initialize()`
Upsert	`INSERT ... ON CONFLICT (user_id, collection) DO UPDATE`
Transactions	`mergeData()` wraps all inserts in a single transaction
Health check	`SELECT 1 AS ok`

STORAGE_PROVIDER=sqlite
STORAGE_SQLITE_PATH=./data/libredb-storage.db   # default

7.3 PostgreSQL Provider

File: src/lib/storage/providers/postgres.ts Package: pg (connection pool)

Feature	Detail
Pool config	max: 5, idleTimeoutMillis: 30000
SSL behavior	`sslmode=disable` for local/non-SSL servers, `sslmode=require` for cloud servers
Upsert	`INSERT ... ON CONFLICT (user_id, collection) DO UPDATE`
Transactions	`mergeData()` uses `BEGIN`/`COMMIT`/`ROLLBACK` with client checkout
Health check	`SELECT 1 AS ok`

STORAGE_PROVIDER=postgres
STORAGE_POSTGRES_URL=postgresql://user:pass@localhost:5432/libredb?sslmode=disable

7.4 Factory

File: src/lib/storage/factory.ts

The factory uses the Singleton pattern — one provider instance per process, lazy-initialized on first access:

getStorageProviderType()     // → 'local' | 'sqlite' | 'postgres'
isServerStorageEnabled()     // → true if not 'local'
getStorageConfig()           // → { provider, serverMode }
getStorageProvider()         // → ServerStorageProvider | null (singleton)
closeStorageProvider()       // → cleanup for testing

Provider classes are dynamically imported — SQLite and PostgreSQL dependencies are only loaded when their provider is selected.

8. API Routes

All routes (except /config) require JWT authentication. The authenticated user's username (email) is used as the user_id for storage scoping.

Endpoint	Method	Auth	Purpose
`/api/storage/config`	GET	Public	Runtime storage mode discovery
`/api/storage`	GET	JWT	Fetch all collections for the authenticated user
`/api/storage/[collection]`	PUT	JWT	Update a single collection
`/api/storage/migrate`	POST	JWT	Merge localStorage dump into server storage

Response Examples

GET /api/storage/config

{ "provider": "sqlite", "serverMode": true }

GET /api/storage

{
  "connections": [{ "id": "c1", "name": "Prod DB", ... }],
  "history": [{ "id": "h1", "query": "SELECT ...", ... }],
  ...
}

PUT /api/storage/connections

// Request: { "data": [{ "id": "c1", "name": "Prod DB", ... }] }
// Response: { "ok": true }

POST /api/storage/migrate

// Request: { "connections": [...], "history": [...], ... }
// Response: { "ok": true, "migrated": ["connections", "history"] }

When STORAGE_PROVIDER=local, all data routes return 404 Not Found (config route always works).

9. Write-Through Cache & Sync Hook

File: src/hooks/use-storage-sync.ts

The hook is mounted in Studio.tsx after useAuth() and orchestrates all client-server synchronization.

Sync States

interface StorageSyncState {
  isServerMode: boolean;     // Server storage active?
  isSyncing: boolean;        // Currently transferring data?
  isReady: boolean;          // Init complete (config fetched + initial pull done)?
  lastSyncedAt: Date | null; // Last successful sync timestamp
  syncError: string | null;  // Last error message (null = healthy)
}

Lifecycle

App Mount
  │
  ├─ GET /api/storage/config
  │   ├─ serverMode: false → done (localStorage only)
  │   └─ serverMode: true ──┐
  │                          │
  │   ┌──────────────────────▼──────────────────────┐
  │   │ Check libredb_server_migrated flag          │
  │   │  ├─ Not migrated → POST /api/storage/migrate│
  │   │  │   (send all localStorage → server merge) │
  │   │  │   Set flag in localStorage               │
  │   │  └─ Already migrated → skip                 │
  │   └──────────────────────┬──────────────────────┘
  │                          │
  │   ┌──────────────────────▼──────────────────────┐
  │   │ Pull: GET /api/storage                      │
  │   │  → Write server data into localStorage      │
  │   │  → Components re-render from localStorage   │
  │   └──────────────────────┬──────────────────────┘
  │                          │
  │   ┌──────────────────────▼──────────────────────┐
  │   │ Listen: 'libredb-storage-change' events     │
  │   │  → Collect pending collections              │
  │   │  → Debounce 500ms                           │
  │   │  → PUT /api/storage/[collection] for each   │
  │   └─────────────────────────────────────────────┘
  │
  ▼ (ongoing)

Push Behavior (Debounced)

When any storage.* mutation fires:

Facade writes to localStorage (immediate, synchronous)
Facade dispatches CustomEvent('libredb-storage-change', { collection, data })
Hook captures event, adds collection to pending set
After 500ms of no new mutations, hook flushes:
- Reads each pending collection from localStorage
- Sends PUT /api/storage/[collection] for each

Graceful Degradation

If /api/storage/config fails → stays in localStorage-only mode
If push fails → logs warning, sets syncError, does not block the UI
Components always read from localStorage — no loading states for storage

10. Migration Flow

When a user first enables server mode (or a new user logs in for the first time):

1. Hook detects serverMode = true
2. Checks localStorage('libredb_server_migrated') flag
3. If not migrated:
   a. Reads whichever of the 10 collections exist in localStorage (a fresh browser with none simply sets the flag and skips)
   b. POST /api/storage/migrate with the collected payload
   c. Server calls provider.mergeData() — upserts each collection as a whole blob in one transaction
   d. Sets 'libredb_server_migrated' flag in localStorage
4. Pull: GET /api/storage → overwrite localStorage with server data
5. Subsequent mutations sync normally via push

This ensures existing localStorage data is preserved when transitioning to server mode.

For the operator-facing summary of this behavior, see Migration: Local to Server in Part 1.

11. Configuration

Environment Variables

Variable	Default	Required	Description
`STORAGE_PROVIDER`	`local`	No	Storage backend: `local`, `sqlite`, or `postgres`
`STORAGE_SQLITE_PATH`	`./data/libredb-storage.db`	No	Path to SQLite database file
`STORAGE_POSTGRES_URL`	—	If `postgres`	PostgreSQL connection string (`sslmode=disable` local, `sslmode=require` cloud)

Why Not `NEXT_PUBLIC_*`?

Next.js NEXT_PUBLIC_* variables are inlined at build time as static strings. This means:

Every storage mode would require a separate Docker build
Cannot change storage mode without rebuilding

Instead, the client discovers the storage mode at runtime via GET /api/storage/config. One Docker image supports all modes.

12. User Scoping & Security

Per-User Isolation

Every row in user_storage is scoped by user_id:

(admin@libredb.org, connections) → [{"id":"c1", "name":"Prod DB"...}]
(admin@libredb.org, history)     → [{"id":"h1", "query":"SELECT..."...}]
(user@libredb.org,  connections) → [{"id":"c2", "name":"Dev DB"...}]

user_id = JWT session username (email address)
Client never sends user_id — server always extracts from JWT cookie
Every query includes WHERE user_id = $username — no cross-user access possible

Authentication

/api/storage/config is public — returns only { provider, serverMode }, no sensitive data
All other /api/storage/* routes require a valid JWT session via getSession()
Unauthorized requests receive 401 Unauthorized

# docker-compose.yml
services:
  libredb-studio:
    environment:
      STORAGE_PROVIDER: sqlite
      STORAGE_SQLITE_PATH: /app/data/libredb-storage.db
    volumes:
      - storage-data:/app/data

volumes:
  storage-data:

The Dockerfile includes better-sqlite3 native bindings and creates the /app/data directory.

PostgreSQL Mode

services:
  libredb-studio:
    environment:
      STORAGE_PROVIDER: postgres
      STORAGE_POSTGRES_URL: postgresql://user:pass@db:5432/libredb
    depends_on:
      - db
  db:
    image: postgres:18
    environment:
      POSTGRES_DB: libredb
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass

No volume needed on the app container — data lives in PostgreSQL.

For step-by-step operator instructions (including healthchecks and verification), see Docker under SQLite and Docker Compose (App + PostgreSQL) in Part 1.

14. Adding a New Provider

To add a new storage backend (e.g., MySQL, DynamoDB):

Step 1: Implement the Interface

Create src/lib/storage/providers/your-provider.ts:

import type { ServerStorageProvider, StorageData, StorageCollection } from '../types';

export class YourStorageProvider implements ServerStorageProvider {
  async initialize(): Promise<void> { /* create table */ }
  async getAllData(userId: string): Promise<Partial<StorageData>> { /* ... */ }
  async getCollection<K extends StorageCollection>(
    userId: string, collection: K
  ): Promise<StorageData[K] | null> { /* ... */ }
  async setCollection<K extends StorageCollection>(
    userId: string, collection: K, data: StorageData[K]
  ): Promise<void> { /* upsert */ }
  async mergeData(
    userId: string, data: Partial<StorageData>
  ): Promise<void> { /* batch upsert in transaction */ }
  async isHealthy(): Promise<boolean> { /* SELECT 1 */ }
  async close(): Promise<void> { /* cleanup */ }
}

Step 2: Register in Factory

Update src/lib/storage/factory.ts:

// Add to StorageProviderType
type StorageProviderType = 'local' | 'sqlite' | 'postgres' | 'your-provider';

// Add dynamic import in getStorageProvider()
case 'your-provider': {
  const { YourStorageProvider } = await import('./providers/your-provider');
  instance = new YourStorageProvider(process.env.STORAGE_YOUR_URL!);
  break;
}

Step 3: Add Tests

Create tests/unit/lib/storage/providers/your-provider.test.ts with mocked driver.

That's it — no changes needed to the facade, API routes, sync hook, or any consumer components.

ARCHITECTURE.md — Overall system architecture
OIDC.md — SSO configuration (pairs well with server storage for team deployments)