Level 5: The Communication Layer
How services talk to each other: APIs, message queues, and asynchronous patterns.
Welcome to Level 5
Modern systems are composed of services that need to communicate. The communication layer defines how data flows between components — synchronously via APIs or asynchronously via message queues and events.
What you will learn
| Module | Topic | Core Idea |
|---|---|---|
| 5.1 | REST API Design | Resource modeling, HTTP methods, pagination, versioning |
| 5.2 | GraphQL and gRPC | When REST is not enough |
| 5.3 | Webhooks and Event-Driven APIs | Push vs pull, reliability patterns |
| 5.4 | Message Queues | Kafka, RabbitMQ, SQS — queue vs log semantics |
| 5.5 | Async Patterns | Saga, outbox, choreography vs orchestration |
| 5.6 | Designing for Communication Failure | Retries, backoff, DLQ, idempotency |
| 5.7 | Checkpoint | Design the communication layer for an order system |
Key Takeaway
The communication layer determines how tightly or loosely coupled your services are. Synchronous APIs create direct dependencies; asynchronous messaging creates temporal decoupling. Most systems need both.
Connect
Start with Module 5.1: REST API Design — the foundation of most service communication.