THE GITHTML FIELD GUIDE
Software migration plan template with exit and rollback gates
A migration plan should show what changes, who is affected, and what evidence permits each stage to proceed. Document the current state, target state, compatibility period, verification, rollback limits, and ownership. Treat irreversible data changes as a distinct decision, not as an ordinary deployment step hidden in a checklist.
Inventory the things that must coexist
List producers, consumers, stored data, configuration, and operational tools that depend on the existing behavior. An illustrative migration might rename a required API field while older clients remain active. The plan needs to describe both client versions, not merely the server patch. Attach evidence for the actual callers and mark unknown consumers explicitly. Explain whether the migration concerns source compatibility, runtime compatibility, or stored representation. A diagram can orient readers, but the inventory should remain text so it can be searched and reviewed independently.
Define gates instead of a hopeful timeline
Use stages with entry conditions and exit evidence. For the illustrative field change, stages might introduce the new field, accept both representations, measure remaining old usage, switch supported clients, and remove the old representation only after approval. Do not claim a deployment strategy guarantees safety. Google's canary-release guidance provides background for controlled exposure, while the exact thresholds belong to the system owner. Each stage should state who may proceed and who reviews the evidence. A date alone is not evidence that a compatibility dependency has disappeared.
- Inventory: enumerate known callers and assign unknown ownership before scheduling removal.
- Verification: specify a representative old-client and new-client interaction.
- Decision gate: name the approver and the evidence that must be available.
Write down the point of no return
Explain what rollback restores and what it cannot restore. Returning application code to an older revision may not reverse a destructive schema transformation. Name the recovery prerequisites and reference the team's tested restoration procedure without embedding privileged commands in a public page. Record cancellation conditions, communication recipients, and post-migration cleanup. When exporting this plan as HTML, put current stage and unresolved risks before the historical discussion. Readers reviewing it on a phone should never mistake a draft proposal for authorization to perform the migration.
Sources and further reading
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