Design pluggable backend for adaptive routing state (file → sqlite / redis)

[NayanKanaparthi]

Context

Adaptive routing currently uses file-backed state for simplicity.

This works for single-process experimentation but does not scale to
multi-worker or distributed deployments.

Open problem

Design a pluggable state backend that:

• Is concurrency-safe
• Supports reproducibility and debugging
• Can swap between file / sqlite / redis implementations

Questions

• What state guarantees are actually required?
• How should replay/debugging work?
• What tradeoffs exist between performance and determinism?

This is a systems design problem, not a bug.