Design Patterns Every Backend Engineer Should Know (in Go)
Practical implementation of the most impactful design patterns — Singleton, Factory, Observer, Strategy, and more — with real Go code.
Design patterns are reusable solutions to common software problems. They’re not copy-paste templates — they’re blueprints for structuring your thinking. Here are the most useful ones for backend engineers, implemented in Go.
1. Singleton — One Instance to Rule Them All
Use when you need exactly one shared resource: database pool, config loader, logger.
sync.Once guarantees thread-safe initialization — far cleaner than a double-checked lock.
2. Factory — Decouple Creation from Use
Callers only know about Notifier — you can add new channels without touching existing code.
3. Strategy — Swap Algorithms at Runtime
Use this when the algorithm selection depends on runtime conditions (e.g., small dataset → bubble sort, large dataset → quicksort).
4. Observer — Event-Driven Decoupling
This is the foundation for event-driven microservices — each service subscribes to what it cares about.
5. Repository — Abstract Your Data Layer
The interface lets you swap PostgreSQL for SQLite in tests — no mock frameworks needed.
6. Middleware Chain — Composable HTTP Handlers
When to Use Which Pattern
| Pattern | Use When |
|---|---|
| Singleton | Shared stateful resource (DB pool, config) |
| Factory | Multiple implementations of one interface |
| Strategy | Algorithm varies by condition/config |
| Observer | Decoupled event propagation |
| Repository | Abstract data access from business logic |
| Middleware | Cross-cutting concerns (auth, logging, tracing) |
Patterns are tools, not rules. Apply them when they reduce complexity — avoid them when they add unnecessary indirection to simple problems.