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The plan switches all reads/writes to OrderStore before historical orders are copied, so existing orders will be missing; if an old order is updated in OrderStore before backfill reaches it, the later Postgres bulk copy can overwrite the newer value.

Phase durations total 9 days (2+1+4+2), which contradicts the stated one-week total; no overlap or adjusted schedule is given.

The plan monitors and pages on elevated 5xx but does not define rollback criteria or a path back to Postgres if OrderStore fails.

The 4-day critical backfill phase is assigned to TBD, leaving execution responsibility unowned.

Row counts between OrderStore and Postgres will not match after cutover because new writes are going to OrderStore; the plan does not explain how to account for those writes or detect overwrites.

Phase 2 switches all reads to OrderStore, but Phase 3 (bulk-copy of historical data) hasn't run yet. Any query for an order older than the replication window will return nothing or error.

The plan states downtime is not expected and the switch is a config flip, but never describes what to do if OrderStore degrades or returns errors after the switch. There is no stated procedure to revert reads/writes back to Postgres.

2 + 1 + 4 + 2 = 9 days of phased work. Even on a 7-day calendar week this doesn't fit, and no parallelism between phases is described.

Phase 1 sets up replication of new Postgres writes into a staging queue, but no phase describes applying those queued writes to OrderStore. Writes landing between replication setup and cutover risk being lost.

The backfill is four days of bulk-copy and verification work with owner listed as TBD, making accountability and scheduling coordination unclear for the most time-consuming phase.

Phase 2 switches all reads to OrderStore before Phase 3 copies historical orders, so reads of any pre-migration order will return nothing until the 4-day backfill completes.

Phase durations sum to 9 days (2+1+4+2) but the stated total duration is one week (7 days).

Phase 1 replicates new writes into a staging queue, but nothing describes how production OrderStore receives those writes so it can serve reads after cutover.

Phase 2 monitors error rates and pages on 5xx, but does not define a rollback to Postgres or a failover procedure if the switch is broken.

Phase 3 backfill and verification is critical to data integrity but its owner is still TBD.

Phase 2 switches all reads to OrderStore, but the backfill doesn't start until Phase 3, so for ~4 days every read of a pre-migration order will miss or fail. This contradicts the stated goals of no data loss and no downtime; backfill (or at least read-fallback to Postgres) must precede or accompany the read cutover.

Phase 1 sends new writes to a "staging queue," but no step ever drains or applies that queue into OrderStore, and Phase 4 removes it. Any writes made between replication start and the cutover config flip would be silently dropped unless a queue-drain step is added before or during cutover.

Phases total 2+1+4+2 = 9 working days, but the plan states a total duration of one week. Either the phases need to be compressed/parallelized or the stated duration corrected.

Phase 2 says to "page on any elevated 5xx" but gives no procedure to revert the config flip, re-point traffic to Postgres, or handle a failed/partial backfill. A one-line rollback path (flip config back, since Postgres is still intact until Phase 4) should be explicit.

Phase 3 is the longest and most data-critical phase (bulk copy plus verification) yet is marked "Owner: TBD." It needs a named owner before the migration starts, especially since Phase 4 (dropping the Postgres tables) depends on its verification being done correctly.

Phase 2 switches all reads/writes to OrderStore, but Phase 3 (which populates historical orders) runs afterward, so for up to 4 days the API cannot serve any historical order from OrderStore. Backfill must complete before or concurrently with cutover.

Phase 2 flips all order traffic to OrderStore with only a 2-hour error-rate watch and no documented procedure to revert reads/writes to Postgres if OrderStore misbehaves, corrupts data, or falls over after the monitoring window.

Phase 3 (the bulk historical copy and reconciliation) is the largest and riskiest phase and is assigned to "TBD", leaving the most failure-prone step unowned.

The phases sum to 2 + 1 + 4 + 2 = 9 days, not the stated "one week" (7 days); the schedule is understated and likely unrealistic for a backfill of this size.

The plan jumps straight from "replicate new writes into a staging queue" to live traffic on OrderStore with no period of dual-writing or shadow-reading against Postgres to confirm parity, ordering, and correctness of the new store.