Multi-Region CD

Deploy across regions safely.

Why multi-region CD

Multi-region CD stages deploys to limit blast radius. Naive parallel deploy hits every customer at once; staged rollouts catch problems while they are still contained to a small region.

• Single-region assumption breaks. Multi-region reality per deploy; customers live in many regions, deploys must be region-aware.
• Naive parallel deploy. All-regions-at-once anti-pattern per deploy; a bug hits all customers simultaneously and rollback affects everyone.
• Sequencing reduces blast radius. Staged rollout per deploy; problems caught in the first region do not propagate to subsequent ones.
• Documented sequence per deploy. Explicit region order per deploy; improvised deploys produce improvised incidents.

Region sequencing

Sequencing is small-first, soak-between, large-last. The smallest region absorbs the first risk; the largest sees a validated deploy by the time it ships there.

• Smallest region first. Low-blast-radius canary per deploy; catches obvious breakage with the smallest customer impact.
• SLO soak between regions. 30-60 minute observation per stage lets metrics catch up before promotion to the next region.
• Largest region last. Validated-by-then largest per deploy; by the time the deploy reaches the largest customer base, it has been validated in smaller regions.
• Explicit gate per region. Named promotion criteria per stage catches "we just kept going" autopilot deploys.

Global state coordination

Global state is the hard part. Schema migrations and any cross-region shared state must stay backward-compatible across the deploy window; otherwise old code in one region breaks against new schema in another.

• Database migrations are tricky. Cross-region compatibility constraint per migration; schema changes must be backward-compatible during the multi-region deploy window.
• Two-phase migrations. Forward-compatible deploy, schema change, then code that uses the schema; three steps per migration to keep regions in sync.
• Avoid coordinated migrations. Dual-write or schema-versioning decoupling per migration; less coordination produces more reliability.
• Rollback path per migration. Explicit revert plan per migration catches one-way migrations as risk before they ship.

Automate the sequence

Automation makes sequencing reliable. CD tools support region-by-region pipelines; SLO checks gate promotion; auto-rollback on failure prevents bad deploys from cascading across regions.

• CD tools support sequencing. Spinnaker, Argo Rollouts, custom CD options per org; all support region-by-region pipelines natively.
• Per-region SLO check. Metric-driven gate per stage auto-pauses on regression rather than requiring human watch.
• Auto-rollback on failed region. Failure-triggers-rollback rule per region; pause subsequent regions until investigated.
• Named owner per pipeline. Responsible team per pipeline catches stale or misconfigured rollouts before they ship.

How to roll out

Roll the discipline out in stages. Start with two regions to prove the pattern, expand as the customer base grows, document the operator runbook for incident pause-and-resume.

• Start with two regions. Smallest-and-largest pair per org; get the pattern right before scaling to more regions.
• Add regions as you grow. Sequence expansion per quarter; avoid 10-region pipelines until you have 10-region customer demand.
• Document pause-and-resume runbook. Operator runbook per pipeline; operators will need it during incidents and the runbook is not the time to draft it.
• Quarterly deploy-pattern review. Rollout-quality retrospective per quarter supports continuous improvement of the sequencing.