Java Knowledge Base -

🔹 What is an API Gateway?

An API Gateway is the single entry point for all client requests in a microservices architecture.Instead of allowing clients to directly call each microservice, the gateway acts as a centralized layer that manages, secures, and routes traffic. It acts like a “smart postman”—receiving requests, verifying them, and routing them to the appropriate microservice.

🔹 Why Do We Need an API Gateway?

Simplifies Client Interaction Clients don’t need to know about individual microservices. Instead of calling /users-service, /orders-service, /payments-service, clients just call /api, and the Gateway routes internally. Centralized Security Authentication, authorization, and encryption policies are applied at one place. Prevents exposing every service directly to the internet.

🔹 What is a Load Balancer?

A Load Balancer is a networking component that sits between the client and the server pool. Its main role is to distribute incoming traffic across multiple servers that provide the same service. Without a Load Balancer, a single server may become overwhelmed when too many requests arrive simultaneously.

🔹 When to Use Which?

Choosing between an API Gateway and a Load Balancer depends on the architecture, goals, and type of application you’re building. Let’s explore both in detail: ✅ Use API Gateway If: You are building a Microservices Architecture In a microservices setup, exposing each microservice (Order, Payment, Inventory, etc.) directly to clients is inefficient and insecure.

What is ArrayList?

ArrayList in Java is backed by a dynamic array. It provides fast random access (O(1)) but slower insertions and deletions in the middle or beginning (O(n)). Best choice when read-heavy operations are frequent.