Backend Engineering Methodology
Backend engineering is the craft of building the server-side systems that power applications — APIs, services, data access, integrations, and the runtime behavior that makes the architecture real. This methodology covers the implementation patterns between architecture design (technical-architect) and quality validation (reviewer).
The Backend Engineer's Domain
| You own |
You don't own |
| API implementation — REST/gRPC/GraphQL endpoints, request validation, response formatting, error handling, middleware chains |
API contract and service boundary design — that's the technical-architect |
| Service logic — business rules, workflow orchestration, state management, background job processing |
Deployment pipeline and infrastructure — that's the platform-engineer |
| Database access patterns — query design, connection management, transaction boundaries, N+1 detection, pagination |
Schema design and migrations — that's the data-architect / data-engineer |
| Integration code — third-party API clients, webhook handlers, message queue consumers/producers |
Code review and quality gates — that's the reviewer |
| Observability instrumentation at the service level — structured logging, metrics, tracing hooks |
Observability infrastructure — that's the SRE / platform-engineer |
| Service-level tests — unit tests for business logic, integration tests for API contracts |
Test strategy and automation — that's the QA-engineer |
Reference Files
| Reference |
When to load |
references/api-patterns.md |
Designing or implementing API endpoints — resource modeling, versioning, pagination, error response formats, request validation |
references/service-patterns.md |
Structuring service logic — clean/hexagonal/layered architecture, dependency injection, middleware composition, request lifecycle, background jobs |
references/database-testing.md |
Database access patterns (connection pooling, query optimization, N+1 detection, pagination strategies, transaction boundaries, read/write splitting, replication lag) and service-level testing (unit testing business logic, integration testing API contracts with test containers/WireMock, contract testing with Pact, test fixtures, CI integration) |
references/integration-patterns.md |
Integrating with external systems — retry with backoff, circuit breakers, idempotency keys, webhook verification, message queue consumers |
references/error-handling.md |
Handling errors systematically — classification (client vs server), structured responses, exception handling patterns, observability correlation |
Core Principles
The interface is the contract — API boundaries are service-level contracts. Every endpoint signature, request schema, response format, and error code is a promise to consumers. Breaking changes are coordination problems, not version bumps.
Business logic is the center of gravity — Keep business rules isolated from framework concerns, transport protocols, and infrastructure details. A well-structured service can survive changes to its HTTP library, database driver, and deployment platform.
Handle errors where they make sense — Catch errors at the boundary where you have enough context to handle them meaningfully. Catch too early and you lose context. Catch too late and you can't recover.
Design for failure, not just success — Every external call can fail. Every database connection can drop. Every message can be duplicated. Idempotency, retry, and graceful degradation are not optimizations — they're requirements.
Test at the right level — Business logic gets unit tests. API contracts get integration tests. Service boundaries get contract tests. Each level catches a different class of failure.
1---2name: backend-engineering-23description: Backend engineering methodology — API implementation patterns (REST, gRPC, GraphQL), service architecture (clean/hexagonal/layered), database access patterns, integration and middleware design, error handling, and service-level testing. Language and framework agnostic.4license: MIT5---67# Backend Engineering Methodology89Backend engineering is the craft of building the server-side systems that power applications — APIs, services, data access, integrations, and the runtime behavior that makes the architecture real. This methodology covers the implementation patterns between architecture design (technical-architect) and quality validation (reviewer).1011## The Backend Engineer's Domain1213| You own | You don't own |14|---------|--------------|15| API implementation — REST/gRPC/GraphQL endpoints, request validation, response formatting, error handling, middleware chains | API contract and service boundary design — that's the technical-architect |16| Service logic — business rules, workflow orchestration, state management, background job processing | Deployment pipeline and infrastructure — that's the platform-engineer |17| Database access patterns — query design, connection management, transaction boundaries, N+1 detection, pagination | Schema design and migrations — that's the data-architect / data-engineer |18| Integration code — third-party API clients, webhook handlers, message queue consumers/producers | Code review and quality gates — that's the reviewer |19| Observability instrumentation at the service level — structured logging, metrics, tracing hooks | Observability infrastructure — that's the SRE / platform-engineer |20| Service-level tests — unit tests for business logic, integration tests for API contracts | Test strategy and automation — that's the QA-engineer |2122## Reference Files2324| Reference | When to load |25|-----------|-------------|26| `references/api-patterns.md` | Designing or implementing API endpoints — resource modeling, versioning, pagination, error response formats, request validation |27| `references/service-patterns.md` | Structuring service logic — clean/hexagonal/layered architecture, dependency injection, middleware composition, request lifecycle, background jobs |28| `references/database-testing.md` | Database access patterns (connection pooling, query optimization, N+1 detection, pagination strategies, transaction boundaries, read/write splitting, replication lag) and service-level testing (unit testing business logic, integration testing API contracts with test containers/WireMock, contract testing with Pact, test fixtures, CI integration) |29| `references/integration-patterns.md` | Integrating with external systems — retry with backoff, circuit breakers, idempotency keys, webhook verification, message queue consumers |30| `references/error-handling.md` | Handling errors systematically — classification (client vs server), structured responses, exception handling patterns, observability correlation |3132## Core Principles3334**The interface is the contract** — API boundaries are service-level contracts. Every endpoint signature, request schema, response format, and error code is a promise to consumers. Breaking changes are coordination problems, not version bumps.3536**Business logic is the center of gravity** — Keep business rules isolated from framework concerns, transport protocols, and infrastructure details. A well-structured service can survive changes to its HTTP library, database driver, and deployment platform.3738**Handle errors where they make sense** — Catch errors at the boundary where you have enough context to handle them meaningfully. Catch too early and you lose context. Catch too late and you can't recover.3940**Design for failure, not just success** — Every external call can fail. Every database connection can drop. Every message can be duplicated. Idempotency, retry, and graceful degradation are not optimizations — they're requirements.4142**Test at the right level** — Business logic gets unit tests. API contracts get integration tests. Service boundaries get contract tests. Each level catches a different class of failure.
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