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What is Decision Engine?

Decision Engine is a Rust service that sits between your orchestrator and your list of payment gateways. When a payment comes in, it picks the best available gateway based on rules you configure — priority ordering, success-rate scoring, volume splits, or debit-network gates — and returns the decision over HTTP.

┌─────────────┐     ┌──────────────────┐     ┌─────────────┐
│  Payment    │────▶│  Decision Engine │────▶│  Best       │
│  Request    │     │  (Fast routing)  │     │  Gateway    │
└─────────────┘     └──────────────────┘     └─────────────┘

It runs as a standalone service — no vendor lock-in, no mandatory orchestrator. Your existing stack calls it over HTTP before dispatching to a gateway, and over time it improves decisions using outcome feedback you push back via the score update API.

What it ships today:

• Rule-based routing — define priority rules per merchant using Euclid, Juspay's open rule engine
• Success-rate ordering — gateways ranked dynamically from transaction outcome feedback
• Multi-objective (cost-aware) routing — re-ranks gateways to balance approval rate against per-gateway processing cost, favoring cheaper gateways when they don't meaningfully hurt auth
• Cost data ingestion — learns each connector's real fee from settlement reports and invoices, at a fine-grained per-cluster level, to power cost-aware routing
• A/B testing — split live traffic between a control and variant routing strategy with a guardrail and built-in significance testing
• Autopilot & auto-calibration — background self-tuning of success-rate hedging and bucket size from observed traffic
• Volume splits — distribute traffic across gateways by percentage
• Debit routing gates — per-merchant toggle for debit-network routing
• Downtime detection — auto-excludes gateways that are failing
• Analytics — ClickHouse-backed tables for routing outcomes, decision audit, and experiment results
• Dashboard — React UI for configuring rules and inspecting decisions
• Multi-DB — MySQL and PostgreSQL support
• Team management — invite and manage members per merchant account

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Quick Start

Docker (Recommended)

git clone https://github.com/juspay/decision-engine.git
cd decision-engine
docker compose --profile postgres-ghcr up -d

API is ready at http://localhost:8080. That's it.

For API + dashboard + docs together:

docker compose --profile dashboard-postgres-ghcr up -d

Open:

• API: http://localhost:8080
• Dashboard: http://localhost:8081/dashboard/
• Docs: http://localhost:8081/introduction
• API guide (curl examples): http://localhost:8081/api-refs/api-ref
• API reference (OpenAPI): http://localhost:8081/api-reference

For deployed docs or dashboard environments, use the same paths under your deployed host, e.g. https://<docs-host>/api-refs/api-ref.

CockroachDB

CockroachDB is PostgreSQL wire-protocol compatible, so it runs on the existing postgres build, migrations_pg, and pg_database config — no separate feature or backend. The docker-compose.cockroach.yml overlay swaps the postgresql service for a single-node CockroachDB.

Full local dev (the oneclick.sh flow), with CockroachDB instead of PostgreSQL:

./oneclick.sh --cockroach

The DB is published on host 26257 (CockroachDB's native port) so it coexists with a local PostgreSQL on 5432; --cockroach points the migrator, seed, and backend there automatically.

Docker-only (app runs in-container against the CockroachDB service):

docker compose -f docker-compose.yaml -f docker-compose.cockroach.yml --profile postgres-local up -d

API stays on http://localhost:8080; the CockroachDB DB Console is at http://localhost:8090. For a secure cluster (e.g. CockroachDB Cloud), set pg_sslmode (and pg_ssl_root_cert) under [pg_database] in your config.

From Source

Prerequisites: Rust 1.85+, MySQL or PostgreSQL, Redis, just

git clone https://github.com/juspay/decision-engine.git
cd decision-engine

# Edit config/development.toml with your DB, Redis, and ClickHouse connection details
# (config/development.toml already exists with all required sections)

MySQL (default features):

cargo build --release --features release
diesel migration run   # set DATABASE_URL=mysql://user:pass@host/dbname first
RUSTFLAGS="-Awarnings" cargo run --features release

PostgreSQL:

cargo build --release --no-default-features --features middleware,kms-aws,postgres
just migrate-pg        # sets DATABASE_URL from env or justfile defaults
RUSTFLAGS="-Awarnings" cargo run --no-default-features --features postgres

For the full local dev environment (API + dashboard on port 5173 + docs), run:

./oneclick.sh

This brings up Postgres, Redis, ClickHouse, and Kafka via Docker Compose, runs migrations, and starts the API server and dashboard locally. See Local Setup Guide for full details and options like ONECLICK_KEEP_INFRA=1.

Verify

curl http://localhost:8080/health
# → {"message":"Health is good"}

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Documentation

Resource	Description
Installation Guide	Docker, source build, database setup — end to end
Local Setup Guide	CLI, Docker, Compose profiles, and Helm
MySQL Setup Guide	MySQL-specific walkthrough
PostgreSQL Setup Guide	PostgreSQL-specific walkthrough
API Guide	Copy-paste curl examples for every route family, including cost ingestion, A/B testing, and autopilot
API Reference (Swagger)	Interactive Swagger UI — browse and try every endpoint against the OpenAPI spec
Multi-Objective Routing	Cost-aware post-step that re-ranks gateways on expected value
Configuration Guide	All config options explained
Deep Dive Blog	How the routing logic works
Performance Benchmarks	Throughput and latency of the /decide-gateway endpoint under sustained load

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Architecture

High-Level Flow

Integration Pattern

Decision Engine fits into an existing payment stack without replacing your orchestrator. The orchestrator calls Decision Engine to get a gateway recommendation, then dispatches to that gateway. Card data stays in your vault — Decision Engine never touches it.

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Contributing

Contributions are welcome — bug reports, feature requests, docs, or code.

# Fork & clone
git clone https://github.com/YOUR_USERNAME/decision-engine.git

# Create a branch
git checkout -b feature/your-feature

# Make changes and test
cargo test

# Submit a PR

See CONTRIBUTING.md for guidelines, and check good first issues if you're new to the codebase.

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Community

Platform	Purpose
	Real-time help and discussions
GitHub Discussions	Feature requests and ideas
GitHub Issues	Bug reports

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License

Licensed under GNU AGPL v3.0.

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