Performance Tuning

Priority: P1 (OPERATIONAL)

High-performance patterns and optimization techniques for NestJS applications.

• Adapter: Use FastifyAdapter instead of Express (2x throughput).

• Compression: Enable Gzip/Brotli compression.

  // main.ts
  app.use(compression());
  

• Keep-Alive: Configure http.Agent keep-alive settings to reuse TCP connections for upstream services.

Scope & Dependency Injection

• Default Scope: Adhere to SINGLETON scope (default).
• Request Scope: AVOID REQUEST scope unless absolutely necessary.
  • Pro Tip: A single request-scoped service makes its entire injection chain request-scoped.
  • Solution: Use Durable Providers (durable: true) for multi-tenancy.
• Lazy Loading: Use LazyModuleLoader for heavyweight modules (e.g., Admin panels).

Caching Strategy

• Application Cache: Use @nestjs/cache-manager for computation results.
  • Deep Dive: See Caching & Redis for L1/L2 strategies and Invalidation patterns.
• HTTP Cache: Set Cache-Control headers for client-side caching (CDN/Browser).
• Distributed: In microservices, use Redis store, not memory store.

Queues & Async Processing

• Offloading: Never block the HTTP request for long-running tasks (Emails, Reports, webhooks).
• Tool: Use @nestjs/bull (BullMQ) or RabbitMQ (@nestjs/microservices).
  • Pattern: Producer (Controller) -> Queue -> Consumer (Processor).

Serialization

• Warning: class-transformer is CPU expensive.
• Optimization: For high-throughput READ endpoints, consider manual mapping or using fast-json-stringify (built-in fastify serialization) instead of interceptors.

Database Tuning

• Projections: Always use select: [] to fetch only needed columns.
• N+1: Prevent N+1 queries by using relations carefully or DataLoader for Graph/Field resolvers.
• Connection Pooling: Configure pool size (e.g., pool: { min: 2, max: 10 }) in config to match DB limits.

Profiling & Scaling

• API Overhead vs DB Execution: Use an "Execution Bucket" strategy to continuously benchmark Total Duration, DB Execution Time, and API Overhead.
  • Total Baseline: Excellent (< 50ms), Acceptable (< 200ms), Poor (> 500ms). Exception: Authentication routes (e.g. bcrypt/argon2) should take 300-500ms intentionally.
  • DB Execution Baseline: Excellent (< 5ms), Acceptable (< 30ms), Poor (> 100ms - implies missing index or N+1 problem).
  • API Overhead Baseline: Excellent (< 20ms), Poor (> 100ms - implies heavy synchronous processing or serialization blocking Node's event loop).
• Offloading: Move CPU-heavy tasks (Image processing, Crypto) to worker_threads.
• Clustering: For non-containerized environments, use ClusterModule to utilize all CPU cores. In K8s, prefer ReplicaSets.

🚫 Anti-Patterns

• Do NOT use standard patterns if specific project rules exist.
• Do NOT ignore error handling or edge cases.