Status: IN
The architecture separates input representations from storage representations: email uses `Email` dataclass for send-time input but stores plain dicts, and KV separates coordinator writes (`local_put` with clock increment) from replication writes (`local_put_raw` with pre-built versions) — enabling internal storage evolution independent of external API.
both decouple the external write representation from internal storage format
Depends on (SL): email-service-input-storage-decoupling, kv-local-put-vs-raw-separation