SQL or NoSQL? When do you choose what? Are migrations needed for MongoDB?

The choice between SQL and NoSQL depends on the project requirements:

• SQL (relational databases):

  • Suitable when data structure is strict and complex relationships between entities are needed.
  • Support for transactions with ACID properties is required.
  • Well-suited for analytics and reporting.

• NoSQL (document, key-value, graph, etc.):

  • Used when flexible schema or rapid scaling is necessary.
  • Suitable for large volumes of unstructured data.
  • May sacrifice consistency for performance (BASE).

Migrations in MongoDB:

Although MongoDB does not require a strict schema, data migrations are still necessary when changing document structures, for example:

• Adding new fields with default values.
• Changing data storage formats.
• Removing outdated fields.

For migrations in MongoDB, scripts in JavaScript or specialized tools (e.g., Mongock) are often used to sequentially update documents in collections.

Thus, migrations are needed, but they are less formalized than in relational databases.