Live coding · 14 min
Mobile live coding interview: what to say while you type
How a mobile live coding round is scored, a 45-minute plan, what to say at each stage, a worked Swift example, and how to recover when you stall.
Interview round · every platform
Mobile coding and live coding interview prep
Most mobile coding rounds are not algorithm puzzles. They are a small, practical feature built while someone watches: a search screen, an image loader, a paginated list. The code matters, and so does whether the interviewer can follow what you are doing.
For: Mobile engineers with a live coding, pair programming or machine coding round scheduled.
What the round scores
| Part of the round | What the interviewer writes down |
|---|---|
| Decomposition | Whether you say the plan, the types and the hard part before you start typing. |
| Working code | The core works, including the case that breaks naive versions: the stale search result, the reused cell, the cancelled load. |
| Communication | Narration the interviewer can follow, and silences that stay short. |
| Testing instinct | Tracing the code with a concrete input and naming the edge cases before saying done. |
| Recovery | What you do when you stall or the interviewer changes a requirement halfway through. |
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
Types in silence for ten minutes, then explains everything at the end.
Strong
Says the plan in one minute, then narrates each decision as it is made.
Weak
Says "done" when it compiles.
Strong
Walks one concrete input through the code and names the two edge cases it does not handle yet.
Weak
Freezes when a hint arrives, or defends the first idea.
Strong
Takes the hint, says what it changes, and keeps moving.
The second question
Follow-ups that decide the round
“The user types fast. Results for an old query arrive after the new ones. What happens?”
Tests cancellation and ordering, the classic trap in a search task.
“Why did you fetch in the initialiser?”
Tests whether you can defend a choice with a trade-off instead of changing it to please the interviewer.
“You have ten minutes left. What do you finish and what do you describe?”
Tests prioritisation under a time box, which a machine coding round scores directly.
How to prepare for it
Know the task family
Read the coding guide for your platform: the tasks that recur and how each is graded.
Record yourself once
45 minutes on a task you have not solved, narrated. Count the silences longer than ten seconds.
Practise with a partner who pushes back
They challenge every other decision; you answer with the trade-off. Then swap roles.
Rehearse the recovery line
One sentence for when you stall, said out loud until it is automatic.
Guides for this round
Live coding · 10 min
Pair programming interview: what gets scored
How a pair programming interview differs from live coding, what the interviewer scores when they type with you, and how to take and give the keyboard.
iOS · 12 min
iOS coding interview: the tasks and how they are graded
What an iOS coding interview asks: the practical tasks that recur, the algorithm round in Swift, and what is graded beyond whether it compiles.
Android · 12 min
Android coding interview: the tasks and how they grade
What an Android coding interview asks: the practical tasks to prepare, the algorithm round in Kotlin, and what is graded beyond a screen that works.
Flutter · 12 min
Flutter machine coding interview: tasks and grading
What a Flutter machine coding interview asks, how the build is graded, and the state and structure choices that decide it before the UI is finished.
iOS · 13 min
iOS mock interview: a full round you can run in 2026
A complete iOS mock interview you can run alone or with a partner: timing, eight prompts with follow-ups, a scoring rubric and how to self-score a recording.
Android · 15 min
Android mock interview: a full script with a rubric
A complete Android mock interview to run alone or with a partner: timings, eight prompts with follow-ups, a scoring rubric and how to self-score a recording.
Books and practice
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.
Architecture
Prepare for the mobile architecture round on iOS, Android and Flutter: module boundaries, dependency direction, state ownership and defending your pattern.
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.