In which cases would you choose a relational database, and in which cases NoSQL solutions? Provide examples from your experience.

Relational databases (RDBs) are chosen when strict data structure, transactional integrity, and complex join queries are important. For example, in financial systems where data accuracy and consistency are crucial, or in CRM systems where data is interconnected and requires complex relationships.

NoSQL solutions are suitable for flexible schemas, large volumes of unstructured data, horizontal scaling, and high write speeds. For example, for logs, real-time analytics, user session storage, or product catalogs with frequently changing structures.

From my experience: for an ERP system, I used PostgreSQL due to complex transactions and relationships between tables. For a project with a large number of user events and analytics, I used MongoDB to quickly store and process JSON documents without a strict schema.