SwiftPay — Real-Time P2P Payment Ledger

Event-driven P2P payments on Java 21 / Spring Boot 3: the gateway accepts transfers (202), settlement runs async over Kafka, and PostgreSQL is the ledger of record. Redis handles idempotency and balance cache on the hot path.

Repo: github.com/Raghav-byte/Swift-pay · License: Non-Commercial

---

Architecture

flowchart LR
  Client[Client / k6]
  GW[payment-gateway :8080]
  Redis[(Redis)]
  PG[(PostgreSQL)]
  K1[[payment-initiated]]
  LS[ledger-service :8081]
  K2[[payment-completed]]
  AW[analytics :8082]

  Client -->|POST /payments| GW
  GW --> Redis
  GW --> PG
  GW -->|after commit| K1
  K1 --> LS
  LS --> PG
  LS --> K2
  K2 --> AW
  AW --> PG

Loading

Gateway validates idempotency + balance, writes PENDING, publishes payment-initiated. Ledger locks accounts, debits/credits, emits payment-completed. Analytics worker aggregates events.

Load-tested at ~250 RPS / ~1M requests — see docs/PERFORMANCE.md.

Full design: docs/SWIFTPAY_ARCHITECTURE.md

---

Quick start

Prerequisites: Java 21, Docker, Postgres (Supabase or local).

1. Create .env at the repo root:

DB_URL=jdbc:postgresql://<pooler-host>:6543/postgres
DB_USERNAME=postgres.<project-ref>
DB_PASSWORD=<your-password>
REDIS_HOST=localhost
REDIS_PORT=6379
KAFKA_BOOTSTRAP=localhost:9092

2. Apply schema + seed — docs/SWIFTPAY_ARCHITECTURE.md §3, docs/seed.sql.

3. Start the stack:

docker compose up -d --build

Compose reads DB_* from .env. For offline Postgres: docker compose --profile local-db up -d and point .env at jdbc:postgresql://postgres:5432/swiftpay.

4. Or run services on the host (after docker compose up -d redis kafka zookeeper):

cd payment-gateway && ./mvnw spring-boot:run
cd ledger-service  && ./mvnw spring-boot:run
cd analytics       && ./mvnw spring-boot:run

5. Try a payment:

curl -X POST http://localhost:8080/v1/payments \
  -H "Content-Type: application/json" \
  -d '{"transactionId":"aaaaaaaa-0000-0000-0000-000000000001",
       "senderId":"b0000001-0000-0000-0000-000000000001",
       "receiverId":"b0000002-0000-0000-0000-000000000002",
       "amount":100.00,"currency":"INR"}'

Swagger: :8080, :8081, :8082 → /swagger-ui.html

Load test: docker compose --profile loadtest run --rm k6 run /scripts/payment-load-test-smoke.js

---

Docs

Doc	Topic
SWIFTPAY_ARCHITECTURE.md	Flows, schema, Redis/Kafka, APIs
PERFORMANCE.md	k6 results
ARCHITECTURE_AND_OPTIMIZATION.md	Tuning notes
k8s/README.md	Kubernetes deploy

---

Copyright © 2026 Raghav. See LICENSE for terms.