LEARN. PRACTICE. GROW.Concept and mechanism
Bicep what-if previews changes and helps discuss effects before deployment. It is neither authorization nor a guarantee of complete coverage. External dependencies and unresolved expressions can prevent analysis of a resource or module; recent tool versions provide diagnostics for these limitations. If the database module was not analyzed, absence of differences in that module does not prove absence of impact. Investigate the missing scope, validate inputs, and obtain additional evidence. A report with many unchanged resources does not compensate for a gap precisely at the critical dependency. Use preview to improve decisions without turning the tool into an approval stamp.
Guided application
In pipeline maintenance, treat unstable tests as problems to investigate. Temporary exclusion needs an owner, deadline, and visible coverage gap; retrying until green and deleting failures distorts evidence. Also measure optimization cost. If restoring and saving a cache takes longer than the avoided work, caching can worsen total time. Versioned templates reduce cross-application drift but need tracked adoption and controlled rollout. Finally, separate waiting from execution: job timeout starts when execution begins, not on queuing. A job within its limit can still miss the release’s overall deadline. Include queues, dependencies, validation, and recovery when planning windows and capacity.
Thirty minutes queued and fifteen executing do not necessarily violate a twenty-minute timeout, but consume 45 minutes of the window.
Common pitfalls
Partial preview as complete; exclusion as repair; cache always faster; timeout as total deadline.
Related topics: Identity, secrets, and pipeline dependencies · Instrumentation and KQL
Make gaps and waiting visible before promising quality or schedule.
Reference: Bicep what-if · AZ-400 objectives 2026-07-27