cloudthinker-ai Zero-Downtime Migration Skill
Execute a zero-downtime migration from {{ source_system }} to {{ target_system }} scheduled for {{ migration_window }}.
Workflow
Phase 1 — Pre-Migration Assessment
PRE-MIGRATION CHECKLIST
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[ ] Source system inventory complete:
- Schema version: ___
- Data volume: ___ GB
- Peak QPS: ___
- Active connections: ___
[ ] Target system provisioned and validated
[ ] Network connectivity verified (source <-> target)
[ ] Schema compatibility confirmed
[ ] Application compatibility tested against target
[ ] Rollback procedure documented and tested
Phase 2 — Dual-Write Configuration
DUAL-WRITE SETUP
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[ ] Change Data Capture (CDC) pipeline configured
[ ] Dual-write proxy or application-level writes enabled
[ ] Write conflict resolution strategy defined:
[ ] Last-write-wins
[ ] Source-priority
[ ] Custom merge logic
[ ] Dual-write monitoring dashboards deployed
[ ] Write latency impact measured:
- Baseline write latency: ___ms
- Dual-write latency: ___ms
- Acceptable threshold: ___ms
Phase 3 — Historical Data Sync
DATA BACKFILL
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[ ] Backfill strategy selected:
[ ] Batch ETL
[ ] Streaming replay
[ ] Snapshot + CDC
[ ] Backfill initiated — start time: ___
[ ] Progress tracking:
- Tables/collections migrated: ___ / ___
- Records processed: ___ / ___
- Estimated completion: ___
[ ] Data integrity verification:
- Row count match: [ ] YES [ ] NO
- Checksum validation: [ ] PASS [ ] FAIL
- Sample record comparison: [ ] PASS [ ] FAIL
Phase 4 — Shadow Read Validation
SHADOW READS
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[ ] Shadow read traffic enabled (read from both, compare)
[ ] Comparison results over 24h window:
- Total reads compared: ___
- Mismatches found: ___
- Mismatch rate: ___%
- Root causes identified for mismatches: [ ] YES
[ ] Performance comparison:
- Source P95 read latency: ___ms
- Target P95 read latency: ___ms
[ ] Shadow reads running clean for ___h (target: 24h minimum)
Phase 5 — Cutover Execution
CUTOVER
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[ ] Final sync lag < 100ms confirmed
[ ] On-call team briefed and standing by
[ ] Communication sent to stakeholders
[ ] Cutover initiated — timestamp: ___
Cutover steps:
[ ] 1. Pause application writes (< 5s window)
[ ] 2. Drain remaining CDC events
[ ] 3. Verify final consistency check
[ ] 4. Switch read/write endpoint to target
[ ] 5. Resume application writes
[ ] 6. Verify writes landing on target system
Total cutover duration: ___s
Phase 6 — Post-Cutover Monitoring
POST-CUTOVER VALIDATION (4h window)
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T+15min:
[ ] Error rates within baseline
[ ] Read/write latency within SLO
[ ] No data corruption signals
T+1h:
[ ] All application features verified
[ ] Background jobs executing correctly
[ ] Replication healthy (if applicable)
T+4h:
[ ] Metrics stable across all dashboards
[ ] No customer-reported issues
[ ] Migration declared SUCCESSFUL / ROLLBACK NEEDED
Phase 7 — Rollback (if needed)
ROLLBACK PROCEDURE
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Trigger criteria:
- Error rate > 5% for 5 minutes
- Data corruption detected
- P95 latency > 3x baseline for 10 minutes
[ ] Switch read/write endpoint back to source
[ ] Re-enable CDC from target to source (reverse sync)
[ ] Verify source system accepting writes
[ ] Notify stakeholders of rollback
[ ] Schedule post-mortem
Rollback deadline: {{ rollback_deadline }}
Counter-Rationalizations
| Shortcut | Counter | Why |
|---|---|---|
| "We can skip some steps for this case" | Adapt the workflow steps, don't skip them | Skipped steps are where incidents and oversights originate |
| "The user seems to already know what to do" | Complete all workflow phases with the user | The workflow catches blind spots that experience alone misses |
| "This is a minor case, full process is overkill" | Scale the process down, don't turn it off | Minor cases become major when unstructured; the process scales, not disappears |
| "I'll fill in the details later" | Complete each section before moving on | Deferred details are forgotten; real-time capture is more accurate |
| "The template output isn't necessary" | Always produce the structured output format | Structured output enables comparison, audit trails, and handoff to other teams |
Output Format
Produce a migration execution report with:
- Migration summary (source, target, timeline, data volume)
- Data integrity results (row counts, checksums, mismatch analysis)
- Performance comparison (latency, throughput before vs after)
- Cutover log (exact timestamps, duration of write pause)
- Final status (SUCCESS / ROLLED BACK) with follow-up actions