Gateway

[TOC]

API Gateway

An API Gateway is a key component in system design, particularly in microservices architectures and modern web applications. It serves as a centralized entry point for managing and routing requests from clients to the appropriate microservices or backend services within a system.

Methods Of Authentication

API Keys
OAuth
JWT(JSON Web Tokens)
LDAP(Lightweight Directory Access Protocol)

API Gateway Workflow

Routing

Directs client requests to the appropriate service based on URL, method, or headers.
Protocol Translation

Converts requests between protocols (e.g., HTTP -> gRPC/WebSocket).
Request Aggregation

Combines multiple backend class into one to reduce round trips.
Authentication & Authorization

Verifies client identity and access permissions.
Rate Limiting & Throttling

Controls request rates to prevent abuse and ensure resource balance.
Load Balancing

Distributes requests across service instances for scalability and availability.
Caching

Stores backend responses to speed up repeated requests.
Monitoring & Logging

Tracks metrics and logs for performance and usage insights.

API Gateway with Microservices

The web application communicates with the API Gateway.
The API Gateway routes requests to the appropriate microservices.
It handles authentication, rate limiting, caching, and other functions.
Error responses are also standardized by the API Gateway.

API Gateway with Monolith

The web application communicates with the API Gateway.
The API Gateway simplifies client interactions and provides security and caching and other features.
It also manages API versioning and error handling.

API Gateway Use Cases

Example 1: Tinder’s API Gateway

High-Level Design

(TAG: Tinder API Gateway)

This design unlocks three critical outcomes:

Faster developer workflows, since most changes require no code, only config.
Stronger security boundaries, because teams own and isolate their gateway instances.
Better reuse, through shared filters and common middleware patterns.

Boot Flow

This design ensures that routing logic executes with minimal overhead. Every decision has already been made. Every route, predicate, and filter is compiled into the runtime graph.

Request Lifecycle

When a request hits a TAG-powered gateway, it passes through a well-defined pipeline of filters, transformations, and lookups before reaching the backend.