Virtually every software shop I've worked at has had most backend code communicating with multiple databases to get the job done. Sometimes those databases were behind [micro]service abstractions and the communication was indirected by RPC/one-way async dispatch. Sometimes it wasn't. But multiple backend datastores' contents were required for most business operations. The only places I've worked with that didn't need that were very, very small (single digits of thousands or fewer users).
Virtually every software shop I've worked at has had most backend code communicating with multiple databases to get the job done. Sometimes those databases were behind [micro]service abstractions and the communication was indirected by RPC/one-way async dispatch. Sometimes it wasn't. But multiple backend datastores' contents were required for most business operations. The only places I've worked with that didn't need that were very, very small (single digits of thousands or fewer users).