asim-altayb

PostgreSQL immutable-ledger constraints

Context: Double-entry audit rows must not be quietly edited after the fact. Where used: https://github.com/asim-altayb/spring-payments-platform

Schema guards

create unique index one_entry_per_side on ledger_entries (transfer_id, direction);
-- direction in ('DEBIT','CREDIT'), amount > 0

asim-altayb

HMAC webhook signing and verification

Context: Downstream bank/partner webhooks must be authenticable. Where used: https://github.com/asim-altayb/spring-payments-platform

Signing

public String sign(String payload) {
 Mac mac = Mac.getInstance("HmacSHA256");

asim-altayb

Spring Security JWT scope configuration

Context: Protect account/transfer APIs with OAuth2 resource-server scopes. Where used: https://github.com/asim-altayb/spring-payments-platform

Filter chain

http.authorizeHttpRequests(auth -> auth
        .requestMatchers("/actuator/health/**", "/openapi.yaml").permitAll()

asim-altayb

Optimistic concurrency and safe retry

Context: Concurrent transfers debiting the same account must not silently clobber balances. Where used: https://github.com/asim-altayb/spring-payments-platform

Pattern

@Entity
class Account {

asim-altayb

Transactional outbox worker with FOR UPDATE SKIP LOCKED

Context: Publish integration events only if the business transaction committed. Where used: https://github.com/asim-altayb/spring-payments-platform

Why

Writing to the DB and calling HTTP/Kafka in the same request loses events on crash after commit or double-sends on retry. The outbox stores the event in the same transaction as the business write; a worker publishes asynchronously.

Claim query

asim-altayb

Spring / PostgreSQL idempotency pattern

Context: Account-to-account transfers must tolerate client retries without moving money twice. Where used: https://github.com/asim-altayb/spring-payments-platform

Pattern

1. Client sends Idempotency-Key + stable client_id.
2. Service looks up (client_id, idempotency_key) first.
3. On miss, insert transfer row under a unique constraint.

asim-altayb

These are my notes on how I got all the basics working end to end.

Laravel API backend and Vue.js frontend are 2 different servers on different public IP addresses and different domains. I am using pure Vue.js on the front end. Most instructions assume Laravel Vue.js is being used which is structured slightly different with different file names and directories.

• Laravel API backend domain name (api.somedomain.com)
• Vue.js frontend domain name (client.somedomain.com)

No database is needed for any of this to work using sync queue. That is only needed in production if/when you use a database queue.

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asim-altayb

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