API gateway concept in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Role of an API Gateway in Microservices Architecture

Which of the following best describes the primary role of an API Gateway in a microservices architecture?

A It stores all the data for microservices and manages database transactions.

B It acts as a single entry point that routes client requests to appropriate microservices and handles cross-cutting concerns like authentication and rate limiting.

C It is responsible for deploying microservices to cloud infrastructure automatically.

D It replaces the need for load balancers by distributing traffic evenly across servers.

💡 Hint

Think about what component manages client requests and common tasks like security in microservices.

An API Gateway serves as a single entry point for clients. It routes requests to the correct microservice and handles tasks like authentication, logging, and rate limiting, which are common across services.

❓ Architecture

intermediate

API Gateway Request Flow

In a system using an API Gateway, what is the correct sequence of steps when a client makes a request?

A 1,2,3,4,5

B 1,3,2,4,5

C 2,1,3,4,5

D 1,2,4,3,5

💡 Hint

Consider the logical order of authentication before routing and response flow.

The client first sends a request to the API Gateway. The gateway authenticates the request, then routes it to the correct microservice. The microservice processes it and returns the response to the gateway, which then sends it back to the client.

❓ scaling

advanced

Scaling API Gateway for High Traffic

Your system uses an API Gateway that is becoming a bottleneck under high traffic. Which approach best improves scalability while maintaining reliability?

A Remove the API Gateway and let clients call microservices directly to reduce overhead.

B Increase the CPU and memory of a single API Gateway instance to handle more requests.

C Deploy multiple instances of the API Gateway behind a load balancer to distribute incoming requests evenly.

D Use a single-threaded API Gateway instance to avoid concurrency issues.

💡 Hint

Think about horizontal scaling and fault tolerance.

Deploying multiple API Gateway instances behind a load balancer allows the system to handle more requests by distributing load and provides fault tolerance if one instance fails.

❓ tradeoff

advanced

Tradeoff of Using API Gateway for Client Requests

What is a common tradeoff when introducing an API Gateway in front of microservices?

A It guarantees zero downtime during deployments without additional effort.

B It eliminates the need for microservices to handle any business logic.

C It reduces security risks by removing authentication from the system.

D It adds an extra network hop which can increase latency but centralizes cross-cutting concerns.

💡 Hint

Consider the impact on request time and system management.

Using an API Gateway adds an extra step in the request path, which can increase latency slightly. However, it centralizes tasks like authentication and logging, simplifying microservices.

❓ estimation

expert

Estimating API Gateway Capacity for Peak Load

Your API Gateway must handle 10,000 requests per second at peak. Each request takes 5 milliseconds of processing time on the gateway. How many API Gateway instances are needed to handle the load without queuing?

A At least 50 instances

B At least 20 instances

C At least 10 instances

D At least 5 instances

💡 Hint

Calculate how many requests one instance can handle per second, then divide total requests by that number.

One instance can handle 1000 ms / 5 ms = 200 requests per second. To handle 10,000 requests per second, 10,000 / 200 = 50 instances are needed.