Choosing the Right Database
Selecting the right database is crucial for your mobile app's success. SQLite is built into iOS and Android, offering lightweight, zero-configuration storage ideal for simple relational data. Realm provides an object-oriented database with fast, real-time sync capabilities, perfect for collaborative apps. Room (Android) offers an abstraction layer over SQLite with compile-time verification and LiveData integration.
Schema Design Principles
Good schema design is fundamental to app performance. Balance normalization to reduce data redundancy with strategic denormalization for faster reads. Use appropriate data types, enforce data integrity with constraints, and maintain clear, consistent naming conventions throughout your schema.
Mobile databases should prioritize read performance since most apps read data far more than they write.
Indexing Strategies
Proper indexing dramatically improves query performance. Index columns used in WHERE clauses, foreign keys for JOIN operations, and create composite indexes for multi-column queries. However, avoid over-indexing as it increases write time and storage. Use EXPLAIN QUERY PLAN to analyze and optimize query performance.
Database Migrations
Handle schema changes gracefully by versioning your database schema and writing migration scripts for each version change. Test migrations thoroughly before release, provide fallback mechanisms for failed migrations, and never delete user data without explicit permission. Room provides automatic migration support, while SQLite requires manual migration handling.
Query Optimization
Optimize queries for mobile constraints by using pagination for large result sets, limiting result counts, avoiding SELECT *, using prepared statements to prevent SQL injection, batching operations when possible, and running heavy queries on background threads to maintain UI responsiveness.
Sync and Conflict Resolution
For apps with cloud sync, implement last-write-wins or custom conflict resolution strategies. Use timestamps or version numbers for conflict detection, consider operational transformation for real-time collaboration, handle offline changes with sync queues, and provide clear user feedback during sync operations.
Security Best Practices
Protect sensitive data by encrypting databases containing sensitive information using SQLCipher for encrypted SQLite databases. Never store passwords in plain text, implement proper access controls, clear sensitive data when users log out, and use secure key storage through Keychain or KeyStore.