Senior and Staff loops · 11 min
Mobile architecture interview questions, any platform
Architecture interview questions that do not depend on the platform: modules, shared code, server-driven UI, flags, old app versions and who owns what.
Interview round · every platform
Mobile architecture interview prep
Architecture rounds rarely ask which pattern is best. They ask why you chose yours, what it costs, and what happens when a second team, a second platform or a second year arrives.
For: Senior engineers whose loop has an architecture or design discussion round, on any mobile platform.
What the round scores
| Part of the round | What the interviewer writes down |
|---|---|
| Boundaries | How modules and layers are split, and which way dependencies point. |
| State ownership | Where the source of truth lives and who is allowed to change it. |
| Trade-offs | What the chosen pattern costs: boilerplate, onboarding time, build time, testability. |
| Change over time | What happens when a second team owns a module, or a feature has to be removed. |
Loops differ by company. This is the common shape of the round in senior mobile loops, not a promise about any one employer.
A weak answer and a strong one
Weak
Names a pattern (MVVM, Clean, TCA, BLoC) and describes its layers.
Strong
Names the problem the pattern solved in a real codebase and the cost the team paid for it.
Weak
Every screen gets every layer.
Strong
Says where the pattern is relaxed on purpose, and why that is safe.
The second question
Follow-ups that decide the round
“Two teams want to share this module. What changes?”
Tests whether your architecture survives a second owner.
“What would you remove from this design if the team were three people?”
Tests whether you can scale a pattern down, not only up.
“Where does the source of truth for this screen live, and who can write to it?”
Tests state ownership, where most architecture bugs start.
How to prepare for it
Pick one real codebase
Describe its architecture in two minutes: boundaries, dependency direction, state ownership.
Write down the cost
For each choice, one sentence on what it cost and one on what it bought.
Rehearse the change
A new team, a removed feature, a second platform: say what moves.
Guides for this round
iOS · 14 min
iOS architecture interview questions: defending a decision
Ten iOS architecture interview questions and how senior answers are scored: MVVM, TCA, navigation, dependency injection, SPM modules, testing.
Android · 14 min
Android architecture interview questions: layers and modules
Ten Android architecture interview questions and how senior answers are scored: layers, the domain layer, UDF, Hilt, modules, navigation and testing.
Flutter · 10 min
Flutter architecture interview questions and costs
Flutter architecture interview questions on layering, state ownership, packages and testing, with the decision each one tests and what it costs a team.
Also for this round
Other rounds
Mobile system design
Prepare for the mobile system design round: offline behaviour, sync, caching, lifecycle and release, and what the interviewer scores at Senior and Staff.
Coding and live coding
Prepare for mobile coding, live coding and pair programming rounds: the tasks that recur, how they are graded, and what to say while you type.
Senior and Staff
What changes in a Senior or Staff mobile interview loop: the follow-up depth, the scope of the design round, and the evidence each level is expected to show.
Swift, SwiftUI and UIKit
Prepare for the Swift, SwiftUI and UIKit rounds of an iOS interview: concurrency and isolation, memory, state and identity, and what each question scores.
Kotlin and Jetpack Compose
Prepare for the Kotlin, coroutines and Jetpack Compose rounds of an Android interview: structured concurrency, Flow, recomposition and state.