What does “a lot of data” in a database mean?

What does “a lot of data” in a database mean?

How much data is considered “a lot”? Is it 100,000 records, 1 million, or even 100 million? Does it depend on whether it’s a gigabyte or a hundred gigabytes? When and why does the performance of a database start to “sag”? It is simply impossible to give a clear answer to these questions.