If your data structure is well-defined and follows a structured schema. If you require complex transactions, relational integrity, and advanced querying capabilities (e.g., complex joins), MySQL might be a better fit. MySQL is a solid choice for applications where data consistency and ACID (Atomicity, Consistency, Isolation, Durability) compliance are critical.
If your data is semi-structured or unstructured, or if it evolves over time. If you need high write scalability, flexibility in schema design, and the ability to store large amounts of data, MongoDB can be a good choice. MongoDB is well-suited for applications with rapidly changing requirements or where data can vary greatly between documents.