[justinclift]

As a data point, it seems to be reasonably common for people to use both SQLite + <some other database> (eg PG).

Probably because they have different use cases that don't overlap too much. eg SQLite is great for single file info storage and passing around. The others - being competing multi user servers - don't do that. :)

[laumars]

Up until very recently I used to regularly hop between sqlite3, Informix (don't hear much about that these days), MySQL (or compatible) and some key/value stores like Redis and memcache. Occasionally used to dip into MSSQL too but that wasn't often.