Banking api for creating accounts and executing monetary transactions between them.
- Default port
8080, can be configured indocker-compose.yml POST /accounts- Creates new account. Balance must be positive or zero.
- In case of validation failures, returns
400 BAD_REQUEST - Request:
{"balance": 100.0} - Response:
{"id": 1, "balance": 100.0}
GET /accounts/{id}/balance- Fetches the balance from existing account.
- In case of validation failures, returns
400 BAD_REQUEST - Response:
100.0
POST /transactions- Creates and executes transaction between two existing accounts.
- Amount should be positive
- Recipient should have enough funds
- In case of validation failures, returns
400 BAD_REQUEST - In case of concurrent data access and version conflicts, returns
409 CONFLICT - Request:
{"amount": 1.0, "from": 1, "to": 2} - Response:
{"id": 1, "amount": 1.0, "from": 1, "to": 2}
- Creates and executes transaction between two existing accounts.
- Kotlin
1.9.10(JVM 17.0.8 Liberica) - Spring
6.0.11, Spring Boot3.1.3 - Spring WebFlux
- Spring Data R2DBC
- Postgres 15
- Testcontainers
- Flyway
- Docker, Docker Compose
./mvnw clean install docker:build
- Docker
- Docker compose plugin
docker compose up -d
docker compose down -v
For the data consistency during concurrent transactions
I decided to use optimistic locking via versioning (@Version Spring annotation).
This creates negative response on concurrent request for the same account
but provides consistency without too much performance overhead on transactions.
Service returns response with HTTP 409 CONFLICT response code in case of such request.
If needed, this request can be retried either on client or on server side.