Cloud Migration Overview and Methodology
Domain scope
This domain tests whether you can treat cloud migration as a portfolio program rather than a server move. You need the vocabulary of drivers, the 6R disposition model, phase gates, and the link from business case to cutover and operations. Questions often ask you to classify workloads, sequence waves, and name the decision owner for a gate.
Core rules
- Begin with measurable outcomes: cost avoidance, resilience, speed, or compliance. A migration without a business case becomes an uncontrolled rehost.
- Assign every application one disposition: rehost, replatform, refactor, repurchase, retire, or retain. Retire and retain are valid outcomes, not failures.
- Use phase gates: assess, plan, migrate, validate, optimize, govern. Each gate needs exit criteria, evidence, and an accountable owner.
- Sequence in waves by dependency, risk, and business calendar. Put low-risk, high-learning workloads first; keep tightly coupled systems together.
- Standardize through a migration factory: templates, runbooks, checklists, and reusable landing-zone patterns.
- Track portfolio readiness, dependency blockers, one-time cost, run-rate change, and risk in one register.
Worked example
A 120-application portfolio is classified as 50 rehost, 30 replatform, 15 refactor, 10 repurchase, 10 retire, and 5 retain. The reasoning is not that 50 applications are equally easy: rehost candidates have no unsupported OS or strict latency dependency; replatform candidates can move to managed database or object storage with minor code change; refactor candidates have strategic value but need product funding; repurchase replaces commodity HR and payroll; retire removes duplicate reporting; retain keeps a latency-sensitive plant system on premises for now. Wave 1 includes retire and simple rehost to build the factory; refactor and repurchase start in parallel because their lead times are longer.
Traps
Treating lift-and-shift as the default strategy; confusing replatform with refactor; skipping the business case; forcing every workload into one wave; and letting the migration factory become a document library with no gate evidence.