AetherPay – A Scalable, Event-Driven Microservices Payment Gateway & Subscription Management SaaS Platform (built entirely in Golang)

High-Level Architecture Overview (MVP)

Microservices (6 core services – each in its own Go module/repo or monorepo sub-folder):

1. Auth Service – User/merchant onboarding, JWT + refresh tokens, multi-tenant isolation (tenant ID in claims), rate-limiting with Redis.

2. Merchant Service – Merchant profiles, API keys, webhooks configuration.

3. Billing Service – Subscription plans, invoices, pricing tiers (uses Postgres + Redis cache).

4. Payment Service – Core transaction processing (mocked gateway), idempotency keys, 3DS simulation.

5. Notification Service – Emails, webhooks, SMS (consumes queues).

6. Analytics Service – Real-time + batch reporting (consumes Kafka events).

Cross-cutting concerns (shared libraries or sidecars):

• API Gateway (custom Go service with Fiber/Gin + middleware or Traefik).

• Internal communication: gRPC (with Protobuf) between services + Kafka for async events.

• Observability: OpenTelemetry + Jaeger (tracing), Prometheus + Grafana (metrics), Zap (structured logging).

Tech Stack (exactly what you asked for + senior essentials):

| Component | Technology | Purpose |

|------------------------|-------------------------------------|--------|

| Language & Framework | Go 1.23+, Fiber/Gin + gRPC | High-performance APIs |

| Messaging (Queue) | RabbitMQ | Reliable background jobs (emails, webhooks, retries) |

| Messaging (Streaming) | Kafka (with Sarama or Franz-go) | Business events (PaymentSucceeded, SubscriptionCreated) for analytics & audit |

| Caching / Rate-limit | Redis (go-redis + Redis Cluster) | Session cache, rate limiting, idempotency store |

| Databases | PostgreSQL (per-service or schema-based multi-tenant) | Transactional data |

| Containerization | Docker + multi-stage builds | Each service + DB + brokers |

| Orchestration | Kubernetes (Helm charts or plain YAML) | Deployments, HPA, StatefulSets, Ingress, Secrets |

| Resilience | github.com/sony/gobreaker + retries + Outbox pattern | Circuit breaking & reliable events |

| Tracing & Metrics | OpenTelemetry + Jaeger + Prometheus | Full observability |

MVP Features (build this first – 4–6 weeks for a solid senior portfolio)

Core User Flows:

1. Merchant registers → gets API key + tenant ID.

2. Merchant creates subscription plans.

3. Customer subscribes → Payment Service processes (mock success/failure).

4. On success:

   • Payment Service publishes Kafka event (PaymentSucceeded).

   • Analytics Service consumes and updates dashboards.

   • Notification Service picks up RabbitMQ task → sends email + fires merchant webhook.

5. Idempotent retry support (same payment request ID → no double charge).

6. Basic merchant dashboard API (list subscriptions, revenue metrics).

Non-functional MVP requirements (what makes it senior):

• Distributed Saga for subscription + payment (orchestrated via Kafka events + compensating actions).

• Outbox Pattern in Payment/Billing services → guarantees events are published even if Kafka is down.

• Horizontal scaling: each service can have 3+ pods.

• Rate limiting (Redis) at gateway + per-tenant.

• Graceful shutdown + zero-downtime deployments (K8s readiness/liveness probes).

• Full observability: trace a single payment request across 5 services.

Full Project Architecture Details (MVP – Production Ready)

1. Repository Structure (Monorepo recommended for ease)

   
   aetherpay/
   
   ├── services/
   
   │   ├── auth/          (Go module)
   
   │   ├── merchant/
   
   │   ├── billing/
   
   │   ├── payment/       ← heaviest service
   
   │   ├── notification/
   
   │   └── analytics/
   
   ├── infra/             ← k8s manifests + Helm
   
   ├── docker-compose.yml ← local dev (all brokers + DBs)
   
   ├── shared/            ← common libs (errors, otel, saga utils)
   
   └── deploy/            ← ArgoCD/GitOps optional for bonus points
   
   

2. Docker + Kubernetes Setup

   • Every service has its own Dockerfile (multi-stage, < 50 MB images).

   • docker-compose.yml for local: includes Postgres (x6 schemas or separate), Redis Cluster, RabbitMQ, Kafka (with Zookeeper or KRaft), Kafka UI, RabbitMQ Management.

   • K8s manifests (or Helm chart):

     • Deployments + HPA (CPU/Memory based autoscaling).

     • StatefulSet for Postgres, Redis, Kafka.

     • ClusterIP Services + Ingress (Nginx or Traefik).

     • ConfigMaps + Secrets (or external-secrets operator).

     • NetworkPolicies for security.

3. Messaging Strategy (why both RabbitMQ + Kafka)

   • RabbitMQ → Task queue (fire-and-forget jobs with dead-letter queues, retries with exponential backoff).

   • Kafka → Durable event log (replayable, exactly-once semantics with transactions, analytics & audit trail).

4. Redis Usage (3 critical patterns)

   • Session + API key cache.

   • Distributed rate limiter (token bucket).

   • Idempotency store (payment request ID → result for 24h).

5. Observability Stack (deploy in K8s)

   • Jaeger for distributed tracing.

   • Prometheus + Grafana dashboards (request latency, error rate, queue depth, Kafka lag).

   • Loki for logs (optional).

6. Security & Senior Touches

   • mTLS between services (optional but impressive).

   • JWT with tenant isolation + OPA/Gatekeeper policies in K8s.

   • All external APIs behind API key + rate limit.

   • Audit logging via Kafka.

How to Build & Showcase It (Senior Portfolio Tips)

• Local dev → docker-compose up.

• Production-like → kubectl apply -f infra/ or Helm.

• Write comprehensive README with:

  • Architecture diagram (draw.io or Excalidraw).

  • Saga flow explanation.

  • How you handled exactly-once delivery.

  • K8s scaling test results (locust or k6 load test).

• Add CI/CD (GitHub Actions) → build, test, scan, push to kind/local cluster.

• Bonus senior points: implement Chaos Engineering (chaos-mesh) to kill pods and show resilience.

This single project lets you speak confidently about every senior Go microservices topic: event-driven architecture, distributed transactions, cloud-native deployment, observability, resilience patterns, and scaling.

Build it, put it on GitHub with a killer README + architecture diagram, and you will stand out massively for Senior Go / Microservices / Backend Engineer roles (especially in fintech, payments, or high-scale SaaS companies).

Start with the Payment + Billing services + Kafka + RabbitMQ integration — that alone will already look senior. Good luck! If you want the exact folder structure, sample Dockerfiles, or Saga implementation skeleton, just ask.