Why Your Agent Needs a Read Replica: Read/Write Splitting for Agent Memory
Most agent memory is one undifferentiated store. The loop reads from it to assemble context at the start of every step, and writes to it after every action — new observations, running summaries, scratchpad edits. Same store, same access path, no separation. It works fine in a demo and starts to rot the moment the agent runs long enough for the store to get large.
The reason it rots is familiar to anyone who has scaled a database. A single store that serves both reads and writes is a single-primary database with no replica, and it inherits every problem that topology has under load: writes contend with reads, a half-written record gets read mid-update, and there is no isolation between the volatile working set and the durable record. We solved this for databases decades ago by splitting reads from writes. Agent memory deserves the same treatment.
The fix is not a bigger vector index or a smarter embedding model. It is an architectural one — recognizing that "memory" is two different workloads wearing the same name, and giving each the storage discipline it actually needs.
