Question 1

What CockroachDB migrations do you handle?

Accepted Answer

PostgreSQL → CockroachDB via MOLT toolkit (the canonical migration path), Oracle → CockroachDB (procedural code rewrites + schema conversion), MySQL → CockroachDB (less common but viable), multi-region table cutovers (REGIONAL BY ROW topology rollout), self-managed → CockroachDB Cloud Serverless or Dedicated onboarding, version upgrades within CockroachDB. For the architecture-decision phase, see CockroachDB consulting.

Question 2

Postgres → CockroachDB — what's the playbook?

Accepted Answer

Sequence: (1) schema audit — DDL gaps (no inheritance, no extensions, limited triggers) need replacement patterns, (2) application audit — Postgres-specific semantics (Read Committed assumptions, sequences vs UUIDs, LISTEN/NOTIFY, advisory locks) need behavioural validation, (3) MOLT Verify to validate row-by-row data parity, (4) MOLT Fetch for initial bulk load, (5) MOLT Replicator for continuous CDC, (6) cutover with replication-lag-monitored gates. Typical mid-size migrations: 8-16 weeks.

Question 3

MOLT — what does it cover and what does it miss?

Accepted Answer

MOLT (Migrate Off Legacy Tools) is CockroachDB's migration toolkit. Covers: schema conversion from Postgres / MySQL / Oracle / SQL Server, bulk data load via MOLT Fetch, continuous CDC replication via MOLT Replicator, row-level parity validation via MOLT Verify. What it misses: complex PL/pgSQL packages (manual rewrite), Postgres-extension dependencies (pgvector, PostGIS need replacement strategy), Oracle PL/SQL packages (largest single piece of Oracle migrations), application-tier semantic differences (Read Committed assumptions, transaction retry handling).

Question 4

Multi-region table cutover — what's the rollout?

Accepted Answer

Multi-region tables (REGIONAL BY TABLE, REGIONAL BY ROW, GLOBAL) are the CockroachDB-specific value over single-primary Postgres. Cutover sequence: (1) provision additional regions, (2) configure replica placement for survival goals (region-survival vs zone-survival), (3) apply ALTER TABLE locality changes during low-traffic window, (4) validate query latency for each locality pattern, (5) update application routing to leverage region-local reads/writes. Most teams roll out per-table rather than cluster-wide.

Question 5

Self-managed → CockroachDB Cloud — economics?

Accepted Answer

Cloud Serverless: consumption-based, multi-tenant, good for variable workloads + early-stage. Cloud Dedicated: single-tenant, predictable cost, full control over node sizing + region placement. Self-managed wins at sustained scale where reserved-instance EC2 beats Cloud Dedicated pricing. We model both before recommending. The migration itself is straightforward — same engine, configuration + region differences.

Question 6

Cutover playbook for zero-downtime?

Accepted Answer

Standard: (1) MOLT Fetch initial load to target, (2) MOLT Replicator starts CDC, (3) wait for replication lag to settle, (4) MOLT Verify row-level parity, (5) flip reads to target — observe error rate + latency, (6) quiesce writes on source briefly, (7) promote target, (8) flip writes, (9) 24-48 hour soak with source kept replicated as rollback, (10) decommission source.

Question 7

Oracle → CockroachDB — when does this make sense?

Accepted Answer

When you specifically need distributed-SQL + serializable isolation + Postgres-protocol compatibility post-migration. Most Oracle migrations go to standard Postgres (Aurora, RDS, Cloud SQL) — see Oracle vs PostgreSQL. CockroachDB is the right Oracle target only when distributed-SQL features are a real requirement, not just 'multi-AZ' HA that Aurora Postgres can deliver.

CockroachDB Migration Services

CockroachDB migrations we handle

CockroachDB migration — common questions

Ready to plan the CockroachDB migration?