Is Roblox reliable for API services?

I've informed myself about saving data lately and there were some people who suggested using an external database. Why? Is Roblox not reliable enough?

API services is reliable. Yes. Saving data must transform a signal to database, the database stores all the datas.

Basically, think about a locker, and lets say 3 is the data, so you put the data inside the locker. When you need the data, you take out the data out of the locker, and transform into another type of signal.

Sorry if I bad at explainment, but this is what I get from the communities:

API (Application Programming Interface) services are, by definition, interfaces that provide a program with a description of how to interact with a system in order to retrieve and/or change the data within it.

Honestly I don't really understands API service, but it stores datas.

If this helped you, please mark this as the answer, thanks.