Kotlin reached 10.8% usage in the 2025 Stack Overflow Developer Survey—standard for Android and growing on the JVM server side (Stack Overflow 2025 Technology). Resumes list “Kotlin” next to every Android role; your interview should test how they ship safely on mobile.
These five questions surface null-safety habits, coroutine discipline, architecture choices, testing, and Java interop—not syntax recitation.
1. “How do you model nullable state so the UI cannot crash on a missing field?”
Strong candidates use sealed classes, explicit loading/error states, and avoid !! except with a documented invariant. Weak answers rely on try/catch around everything.
2. “When do you use coroutines vs callbacks or Rx—and how do you cancel work when the user navigates away?”
Coroutine scope and structured concurrency separate tutorial Kotlin from production Android. Listen for viewModelScope, supervisor jobs, and leak stories they fixed.
3. “Describe the architecture of an app you maintained. What would you simplify today?”
You learn judgment on MVVM, MVI, repositories, and module boundaries. Good answers admit over-engineering or missing layers.
4. “How do you test ViewModels or domain logic without flaking on dispatchers and time?”
Testing questions reveal maturity. Strong candidates mention fakes, test dispatchers, and what they still cover with instrumented tests.
5. “Tell me about Java interop pain in a mixed codebase. What conventions did your team adopt?”
Many teams still ship Java libraries. Good answers cover nullability annotations, SAM conversions, and gradual Kotlin migration—not “we rewrote everything overnight.”
Turn answers into comparable evidence
Log one null-safety pattern, one coroutine story, one architecture tradeoff, and one interop example per finalist.
One scorecard for every finalist
Use the same five questions for each candidate for this opening. Consistent questions support consistent evaluation, which aligns with EEOC guidance for employers to apply the same standards to applicants for the same position (EEOC).
Use Canvider JobCraft to define Kotlin/Android scope in the JD, InterviewGen for gap-based follow-ups, and DecisionHelper to compare finalists on the criteria you published.
Next step: Explore InterviewGen and DecisionHelper, then get started free.