DB Pagination
Offset-Based
SELECT * FROM products ORDER BY id LIMIT 20 OFFSET 20000;
-- Slow at high offsets (scans all skipped rows)
Keyset-Based
SELECT * FROM products WHERE id > 100 ORDER BY id LIMIT 20;
-- Fast at any position
Comparison
| Method | Page 1 | Page 1000 | Consistent |
|---|---|---|---|
| OFFSET | Fast | Slow | No |
| KEYSET | Fast | Fast | Yes |
Key Points
- Understanding Database 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
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Database Best Practices
Design Principles
- Normalize to 3NF, denormalize for performance
- Use appropriate data types
- Add indexes for frequent queries
- Implement proper constraints
Query Optimization
- Use EXPLAIN ANALYZE
- Avoid SELECT *
- Use JOIN instead of subqueries
- Implement pagination
Operations
- Regular backups
- Monitor slow queries
- Implement connection pooling
- Use read replicas for scaling
Key Points
- Understanding Database 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
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Practice Problems
Design and implement a solution for Database Pagination in a backend system. Consider scalability, error handling, and production readiness.
Solution
// Database Pagination implementation
// Key aspects: validation, error handling, logging, testing
public class DatabasePagination {
// Production-ready implementation
}Identify and handle edge cases for Database 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, idempotencyWrite a testing strategy for Database Pagination. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. Offset slows at high pages because?
2. Best for large datasets?
3. What is the primary purpose of Database Pagination?
4. What is a common mistake when implementing Database Pagination?
Flashcards
Question
Offset slow at high pages?
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Answer
Must scan all skipped rows
Question
Best for large datasets?
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Answer
Keyset - constant performance
Question
What is Database Pagination?
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Answer
Database Pagination is a key concept in backend development.
Question
When to use Database Pagination?
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Answer
Use Database Pagination when building production systems that require reliability, scalability, and maintainability.
Question
Database 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 degrades at high offsets
- 2.Keyset is constant performance
- 3.Use indexed column for keyset
Interview Tips
- •Compare offset vs keyset
- •Know when to use each
Cheat Sheet
DB Pagination
- Offset: LIMIT + OFFSET (slow at high pages)
- Keyset: WHERE id > last_id (constant)
- Large data: keyset preferred