What's the lifetime of agent instance

I want to build a http server to provide an api, that people can use my crew easily. But I don’t know the lifetime of those objects(crew agent task), like:

  1. Should I create a singleton for those objects or I must create new ones each time.
  2. Are those method thread-safe since there may some concurrent requests(they may operate memory module at the same time)?
  3. What’s the difference between crewai-memory and session-history in other framework.

I think creating new instances every time is better and more predictable if you are using via an API