What long term memory architectures for agent and underlying infrastructure are you using?

I have seen a lot of different ways of implementing long term memory for agents and curious to know which mechanism works better for different usecases and what infrastructure are people using.

For me the architecture that has been most robust but more token heavy is agent as memory controller and is built on neon postgres - agent has tools to add memory entries with tools (save, list, update, delete, search) represented as heirarchial directory memories/topic/sub-topic.md backed by serverless postgres for it's scale to zero, instant branching for evals/debugging etc