OLTP (Online Transaction Processing)

OLTP is the kind of database that runs an app's day-to-day business: it records many small, fast changes such as a customer placing an order, transferring money, or updating a profile. Each operation touches just a few rows and must finish in milliseconds, so the database is tuned for quick, reliable writes rather than big analyses.

It matters because OLTP is where your raw operational data is born — the system of record. The catch is that running heavy analytical questions (“what were total sales by region last year?”) directly against an OLTP system is slow and can hurt the live app, which is exactly why analysts copy the data out into a separate analytical system instead.