Portfolio ↗

Cutover Planning

Rehearsals, go/no-go criteria and a rollback that has been executed.

4Questions
11Flashcards
4Terms
Drill this topic All of Legacy Modernization
Questions

4 to work through

  1. intermediate

    A cutover is planned for a Sunday night. What must be prepared beyond the technical steps, and what is the most commonly missing item?

    2 min answer
  2. intermediate

    A platform must cut over a critical service. What does a cutover plan need beyond the switching steps?

    2 min answer
  3. intermediate

    What is in a cutover plan besides the steps, and what would you rehearse?

    1 min answer
  4. advanced

    Alibaba Cloud reported a peak of 583,000 orders per second during Singles' Day on 11 November 2020. Your own platform is far smaller but its annual peak is roughly 40 times a median day and its date is known a year in advance. How does that one fact reshape an eighteen-month migration plan?

    3 min answer
Terminology

4 terms in this topic

practice

Cutover Planning

The plan for the moment of switching — including the decision points, the rollback, and the rehearsal that makes it survivable.

 practice

Cutover Runbook

The step-by-step plan for a migration event, including verification points, decision criteria and the rollback path, rehearsed before it is used.

 practice

Point of No Return

The step in a migration after which rollback would lose data or state - identified in advance, with a named authoriser and a stated recovery plan bey…

 case-study

TSB 2018: A Big-Bang Migration That Was Not Reversible

A UK bank moved millions of customer accounts to a new platform in a single weekend cutover, and the failure locked customers out for weeks.
Legacy Modernization

Neighbouring topics

Legacy Modernization

General material on modernising existing systems.

3 quiz 10 cards 6 terms

Legacy Assessment

Understanding what a system does before deciding what to do with it.

4 quiz 9 cards 2 terms

The Six Rs

Rehost, replatform, refactor, repurchase, retire, retain — per application.

3 quiz 8 cards 4 terms

Rehosting

Lift and shift: fastest, cheapest, and capturing none of the benefits.

4 quiz 9 cards 3 terms

Replatforming

Targeted changes that capture operational wins without a rewrite.

3 quiz 10 cards 3 terms

Refactoring & Re-architecting

Changing structure incrementally while the system keeps running.

4 quiz 8 cards 2 terms

Rebuild vs Re-architect

Why greenfield replacement fails, and the narrow cases where it does not.

5 quiz 7 cards 2 terms

Strangler Fig

Routing capabilities to new implementations behind a facade, one at a time.

5 quiz 7 cards 4 terms

Application Decomposition

Finding seams in a monolith, starting from the data.

4 quiz 10 cards 4 terms

Database Migration

Moving engines, versions and schemas without losing data or uptime.

5 quiz 12 cards 3 terms

Data Migration Strategies

Backfill, dual-write, reconciliation and verification.

5 quiz 11 cards 3 terms

Zero-Downtime Migration

Expand, migrate, contract — and the contract phase that never happens.

4 quiz 10 cards 3 terms

Parallel Run

Shadowing the old system to discover the rules nobody documented.

4 quiz 10 cards 4 terms

Legacy Integration Patterns

Anti-corruption layers, adapters and CDC against systems that cannot change.

4 quiz 9 cards 3 terms

Mainframe Modernization

Batch windows, COBOL, and the risk profile of core banking systems.

5 quiz 9 cards 3 terms

Migration Risk

Bounding blast radius, staging by cohort, and honest readiness reporting.

5 quiz 11 cards 2 terms

Modernisation Business Case

Pricing tail risk so deferred maintenance becomes fundable.

4 quiz 8 cards 3 terms

Coexistence Patterns

Running old and new together for years without corrupting either.

4 quiz 9 cards 3 terms

Decommissioning

Actually switching the old system off, and proving nothing depended on it.

3 quiz 9 cards 5 terms