Gontse Sebolai/JHB/2026
Project laboratory

Financial transaction event platform · Java flagship

Mercator
Relay

A financial-transaction event platform that makes idempotency, delivery state and controlled failure visible—from HTTP intake to Kafka and the audit ledger.

Java 21Spring Boot 4.1Kafka 4.3Angular 22Terraform 1.15
Gontse portrayed full-length as a Renaissance cartographer tracing a route in a period studiolo
Full-scene identity study · period clothing, environment and working pose generated as one composition.
06

backend integration tests

PostgreSQL and Kafka Testcontainers

Evidence item 1
03

Angular tests

selection, filtering and local command state

Evidence item 2
04

browser checks

desktop/mobile flow, overflow and axe

Evidence item 3
02

Terraform contracts

mocked provider; no AWS account

Evidence item 4

The engineering decision

Prove the failure path before adding scale.

The first slice stays in one modular deployable. Package boundaries are explicit, while independent services wait for a real deployment or scaling reason.

  1. 01Accept

    Validate the envelope and bind an idempotency key.

  2. 02Commit

    Write the event, audit entry and outbox intent atomically.

  3. 03Publish

    Claim pending outbox rows and route them through Kafka.

  4. 04Deliver

    Dedupe per destination or exhaust into the dead-letter path.

Stack selected from employer evidence

Learning breadth with a reason.

The stack responds to recurring Java, messaging, Angular, cloud and infrastructure-as-code signals in current target-employer material. It is not a collection of tools added only for novelty.

01

Java 21 + Spring Boot 4.1

Enterprise Java depth separate from the .NET flagship.

02

PostgreSQL + Flyway

Database constraints carry idempotency, audit and delivery history.

03

Kafka 4.3.1

At-least-once routing, bounded retries and a visible dead-letter path.

04

Angular 22 + signals

A second frontend ecosystem with strict TypeScript and browser evidence.

05

Terraform + AWS contract

Private ECS, encrypted RDS and IAM-authenticated MSK, tested without apply.

Atomic persistence

Event, audit and outbox intent commit together.

Observable routing

Publish, retry and dead-letter transitions remain inspectable.

Real dependencies

Testcontainers exercises PostgreSQL and Kafka, not substitutes.

Cloud contract

Terraform is mocked and tested; a paid deployment is not implied.

Verified locally; bounded honestly.

Docker health, one complete delivery route, Prometheus output and npm audit were checked in the 15 July 2026 local checkpoint. The backend Testcontainers and control-room checks were refreshed on 07 September 2026. The AWS design has not been applied, and the Angular replay control does not claim a backend command that does not exist.

Docker route reached DELIVERED · 15 July checkpoint

No serious/critical axe findings · 15 July checkpoint

npm audit reported 0 vulnerabilities · 15 July checkpoint

Terraform provider mocks only

Discuss the build View Lumen Observatory

Local repository and noindex; not presented as a deployed production system.

Backend Testcontainers and control-room verification refreshed 07 September 2026: 6 integration tests, 3 Angular checks, a build and 4 browser checks. Terraform remains dated 15 July 2026; no AWS apply is claimed.