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Pagination

Implement offset, cursor, and keyset pagination for list endpoints.

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Pagination Types

Offset-Based Pagination

GET /products?page=2&limit=20

Response:
{
  "data": [...],
  "pagination": {
    "page": 2,
    "limit": 20,
    "total": 150,
    "totalPages": 8
  }
}

SQL: SELECT * FROM products LIMIT 20 OFFSET 20;

Pros: Simple, supports "jump to page"
Cons: Inconsistent with concurrent inserts/deletes

Cursor-Based Pagination

GET /products?limit=20&cursor=eyJpZCI6MTIzfQ==

Response:
{
  "data": [...],
  "pagination": {
    "nextCursor": "eyJpZCI6MTQzfQ==",
    "hasMore": true
  }
}

SQL: SELECT * FROM products WHERE id > 123 LIMIT 20;

Pros: Consistent, performant on large datasets
Cons: Can't jump to specific page

Keyset (Seek) Pagination

GET /products?sort=created_at,id&after=2025-01-15T10:00:00Z&limit=20

Comparison

Type Jump to Page Consistent Performance Complexity
Offset Yes No Degrades at offset Low
Cursor No Yes Constant Medium
Keyset No Yes Constant High

Pagination Best Practices

Types

  • Offset: Simple, but slow for large offsets
  • Cursor: Consistent, better performance
  • Keyset: Composite key ordering

Response Format

{
  "data": [...],
  "pagination": {
    "page": 1,
    "pageSize": 20,
    "total": 100,
    "hasMore": true
  }
}

Best Practices

  • Default page size: 20-50
  • Maximum page size: 100
  • Use cursor for large datasets

Key Points

  • Understanding Pagination is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0/3solved
Implement Pagination

Design and implement a solution for Pagination in a backend system. Consider scalability, error handling, and production readiness.

Solution
// Pagination implementation
// Key aspects: validation, error handling, logging, testing

public class Pagination {
    // Production-ready implementation
}
Pagination Edge Cases

Identify and handle edge cases for Pagination. What happens under high load, with invalid input, or during failures?

Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Pagination Testing Strategy

Write a testing strategy for Pagination. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Which pagination type degrades performance at high offsets?

Question 1 options

2. For a social media feed, which pagination is best?

Question 2 options

3. What is the primary purpose of Pagination?

Question 3 options

4. What is a common mistake when implementing Pagination?

Question 4 options

Flashcards

Question

Offset vs cursor pagination?

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Answer

Offset: page number, can jump. Cursor: consistent, can't jump.

Question

When to use cursor pagination?

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Answer

Large datasets, real-time feeds, streaming

Question

What is Pagination?

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Answer

Pagination is a key concept in backend development.

Question

When to use Pagination?

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Answer

Use Pagination when building production systems that require reliability, scalability, and maintainability.

Question

Pagination best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.Offset-based: simple but degrades at high offsets
  • 2.Cursor-based: consistent and performant, can't jump to page
  • 3.Choose based on use case: admin panels=offset, feeds=cursor
  • 4.Always include total count or hasMore flag

Interview Tips

  • •Compare offset vs cursor pagination
  • •Know when to use each type

Cheat Sheet

Pagination

  • Offset: ?page=2&limit=20 (simple, degrades)
  • Cursor: ?cursor=abc&limit=20 (consistent, performant)
  • SQL Offset: LIMIT 20 OFFSET 20
  • SQL Cursor: WHERE id > 123 LIMIT 20
  • Admin panels: Offset, Feeds: Cursor