Measure how long your rollback actually takes

short · 40 min · Objective 2.3

Task

Write a cutover plan with a rollback, then TIME the rollback. A rollback that takes longer than the remaining window is not available to you, and the only way to know is to have done it once.

Steps

  1. Run a small service in container A, with a name resolving to it. Confirm a client reaches it by name.
  2. Write lab/cutover.md: the timeline, the point of no return marked explicitly, the go/no-go criteria, the named decision maker, and the rollback trigger agreed in advance.
  3. Stand up container B with the same service and a copy of the data. Cut over by changing the name to point at B, and time how long the client takes to follow -- then repeat the measurement with a long TTL and with a short one, and record both.
  4. Write a record to B so the two now differ. Then execute the rollback and time it, recording in lab/rollback.md what happened to the record written at B.
  5. Write the sentence stating where the real point of no return was, and compare it against the one you wrote in step 2.

Verify

grep -Eci 'ttl' lab/cutover.md lab/rollback.md
grep -Ec '[0-9]+ ?(s|sec|second|min)' lab/rollback.md
grep -Eci 'point of no return|first write' lab/rollback.md

A measured rollback duration must appear. The TTL comparison is the point of step 3: the long TTL slows the rollback, which is when speed actually matters.

This is an independent study companion for CompTIA Cloud+ CV0-004 and is not produced by or endorsed by CompTIA.