RDBMS
Relational databases such as PostgreSQL, MySQL, and SQL Server are useful when data has clear relationships, transactions, consistency requirements, and structured queries.
Firebase and Cloud Databases
Firebase Firestore is useful for realtime applications, fast prototyping, serverless apps, and apps that need flexible document-based data structures.
Elasticsearch
Elasticsearch is commonly used for search-heavy systems, log analysis, filtering, full-text search, and analytics use cases.
Local Database for Web Apps
Web apps can store data locally using LocalStorage, IndexedDB, SQLite through WebAssembly-based tools, or libraries like sql.js. This is useful for offline-first apps, PWA features, caching, and local-first experiences.