The last couple places I worked also had a queueing system for async execution/background tasks. A lot of apps use an "AI" or "machine learning" component whic

The last couple places I worked also had a queueing system for async execution/background tasks. A lot of apps use an "AI" or "machine learning" component which usually just means a second heterogeneous internal service. For a little bit larger companies it's pretty common to have a data analytics or data warehouse component. In addition, a web server + database usually require some monitoring system. After you have more than a handful of servers, probably also log aggregation. If you're just a single or handful of people working on something, you probably don't need any of that. Once you get a little bigger (or downtime becomes expensive) those things get tacked on quickly.