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Database Indexes

Understand indexes and their impact on query performance.

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Database Indexes

What Is an Index?

Speeds up reads at cost of writes/storage.

CREATE INDEX idx_product_name ON products(name);

When to Add/Skip

ADD: WHERE, JOIN, ORDER BY columns, high cardinality
SKIP: Small tables, low cardinality, write-heavy

Composite Index

CREATE INDEX idx_cat_price ON products(category_id, price);
-- Works for: WHERE category_id = 1 AND price > 100

Key Points

  • Understanding Database Indexes 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

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 Indexes 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 Database Indexes

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

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

public class DatabaseIndexes {
    // Production-ready implementation
}
Database Indexes Edge Cases

Identify and handle edge cases for Database Indexes. 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
Database Indexes Testing Strategy

Write a testing strategy for Database Indexes. 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. When to add index?

Question 1 options

2. Index tradeoff?

Question 2 options

3. What is the primary purpose of Database Indexes?

Question 3 options

4. What is a common mistake when implementing Database Indexes?

Question 4 options

Flashcards

Question

When add index?

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Answer

WHERE, JOIN, ORDER BY columns

Question

Index tradeoff?

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Answer

Faster reads, slower writes

Question

What is Database Indexes?

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Answer

Database Indexes is a key concept in backend development.

Question

When to use Database Indexes?

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Answer

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

Question

Database Indexes 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.Indexes speed up reads
  • 2.Add on WHERE/JOIN/ORDER BY columns
  • 3.Skip on small tables, low cardinality

Interview Tips

  • •Know when to add/skip indexes
  • •Explain tradeoffs

Cheat Sheet

Indexes

  • Speed up reads, slow writes
  • Add: WHERE, JOIN, ORDER BY
  • Skip: small, low cardinality, write-heavy