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Anubhav Sharma
Anubhav Sharma

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The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

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1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 20 Mar 2026
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Designing an API for a large system requires planning, scalability, security, versioning, and maintainability. In interviews, this question checks your system design knowledge, not only coding.

1. Follow RESTful API Design Principles

Use standard HTTP methods.

Method Use
GET Read data
POST Create
PUT Update
DELETE Remove

Example:

GET /api/users
GET /api/users/10
POST /api/users
PUT /api/users/10
DELETE /api/users/10
  • Easy to understand
  • Standard
  • Scalable

2. Use Layered Architecture (Important for Large System)

Large systems should follow:

Controller → Service → Repository → Database

Example in .NET

UserController
UserService
UserRepository
Database

Benefits:

  • Separation of concerns
  • Easy to maintain
  • Easy to test
  • Good for large teams

3. Use API Versioning (Very Important)

Large systems must support multiple versions.

Example:

/api/v1/users
/api/v2/users

In .NET Core:

[ApiVersion("1.0")]
[Route("api/v{version:apiVersion}/users")]

Why needed?

  • Old apps should not break
  • New features can be added

4. Use Authentication & Authorization

For large systems use:

  • JWT Token
  • OAuth
  • Identity Server

Example:

Authorization: Bearer token

Security rules:

  • Use HTTPS
  • Validate token
  • Use role-based access

5. Use Proper Error Handling

Return standard response.

Good format:

{
  "success": false,
  "message": "User not found",
  "code": 404
}

Use:

  • Global Exception Middleware (.NET Core)
  • Filters (MVC)

6. Use Logging & Monitoring

Large systems must track errors.

Use:

  • Serilog
  • NLog
  • ELK
  • Application Insights

Log:

  • Request
  • Response
  • Errors
  • Exceptions

7. Use Pagination for Large Data

Wrong

GET /api/users

Correct

GET /api/users?page=1&pageSize=20

Benefits:

  • Fast response
  • Less memory
  • Good performance

8. Use Caching

For large systems caching is required.

Use:

  • Redis
  • MemoryCache
  • Distributed cache

Example:

GET /api/config

Cache result.

9. Use Async & Background Processing

For heavy work use:

  • Queue
  • Background service
  • Hangfire
  • RabbitMQ

Example:

  • Email sending
  • Report generation
  • File processing

10. Use Microservices (For Very Large System)

Instead of one big API:

User API
Order API
Payment API
Notification API
Auth API

Benefits:

  • Scalable
  • Independent deployment
  • Easy to maintain

11. Use API Gateway (Enterprise Level)

Large systems use API Gateway.

Example:

Client → API Gateway → Microservices

Benefits:

  • Security
  • Routing
  • Rate limit
  • Logging

12. Follow Naming Convention

Good:

/api/users
/api/orders
/api/products

Bad:

/getUserData
/doSomething

Use nouns not verbs.

13. Performance Optimization

Use:

  • Index in DB
  • DTO instead of entity
  • Select only needed fields
  • Compression
  • Async calls
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