Patterns

35 items

System Design Pattern

API & Gatewayapi-gatewayroutingaggregationauthenticationrate-limitingintermediate

API Gateway Pattern

Single entry point for all client requests

Used in: Kong, AWS API Gateway, Nginx|20 min read

Summary

An API Gateway is a single entry point for all client requests to a microservices architecture. It sits between clients and backend services, handling cross-cutting concerns like authentication, rate limiting, request routing, response aggregation, protocol translation, and monitoring. Instead of each client knowing about dozens of microservices, they interact with one gateway that orchestrates backend calls. This pattern is essential for microservices as it reduces client complexity, enforces security uniformly, and provides a central point for observability.

Key Takeaways

Single Entry Point

All client requests flow through one gateway instead of calling dozens of microservices directly. Gateway routes requests, enforces policies, and shields internal architecture from clients.

Cross-Cutting Concerns

Handle authentication, authorization, rate limiting, logging, monitoring, and metrics in one place instead of duplicating across every microservice.

Request Aggregation

Gateway can aggregate multiple backend calls into one client request. Example: /api/user-dashboard calls user-service, orders-service, and recommendations-service, returns combined response.

API Gateway Pattern

Gateway Responsibilities:

Authentication/Authorization: Validate tokens, check permissions
Rate Limiting: Prevent abuse, enforce quotas
Request Routing: Route to appropriate backend
Load Balancing: Distribute across service instances
Response Caching: Cache common responses
Request/Response Transformation: Adapt formats
Monitoring & Logging: Centralized observability
Circuit Breaking: Protect against cascade failures

Summary

Key Takeaways

Single Entry Point

All client requests flow through one gateway instead of calling dozens of microservices directly. Gateway routes requests, enforces policies, and shields internal architecture from clients.

Cross-Cutting Concerns

Handle authentication, authorization, rate limiting, logging, monitoring, and metrics in one place instead of duplicating across every microservice.

Request Aggregation

Gateway can aggregate multiple backend calls into one client request. Example: /api/user-dashboard calls user-service, orders-service, and recommendations-service, returns combined response.

Protocol Translation

Expose RESTful HTTP to clients while backends use gRPC, GraphQL, or other protocols. Gateway handles translation and serialization.

Single Point of Failure Risk

Gateway is critical path for all traffic. If it goes down, entire system is unavailable. Must run multiple replicas with load balancing.

Latency Overhead

Every request adds gateway hop latency (5-20ms). For latency-sensitive applications, this overhead must be managed carefully.

Pattern Details

API Gateway Pattern

Gateway Responsibilities:

Authentication/Authorization: Validate tokens, check permissions
Rate Limiting: Prevent abuse, enforce quotas
Request Routing: Route to appropriate backend
Load Balancing: Distribute across service instances
Response Caching: Cache common responses
Request/Response Transformation: Adapt formats
Monitoring & Logging: Centralized observability
Circuit Breaking: Protect against cascade failures

Trade-offs

Aspect	Advantage	Disadvantage

Patterns

Horizontal Scaling Pattern

Retry with Backoff Pattern

Queue-based Load Leveling Pattern

Replication Pattern

Caching Strategies Pattern

Fan-out Pattern

Fan-in Pattern

Persistent Connections Pattern

Load Balancing Pattern

Circuit Breaker Pattern

Bloom Filters Pattern

Time-Series Storage Pattern

Bulkhead Pattern

Batch Processing Pattern

Write-Ahead Log Pattern