PhonePe Mobile App Development Interview Questions & Answers
Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About PhonePe hiring for Mobile App Development roles
PhonePe is an Indian digital payments and financial services company, majority-owned by Walmart, known for UPI payments, insurance and investment distribution, and the Pincode commerce app. Its engineering teams build high-scale payments systems. It hires for software engineers, SDETs, data analysts, data engineers and data scientists.
For Mobile App Development roles, this PhonePe practice set focuses most on App Store and Play Store Publishing (7), Mobile Development Fundamentals (6), Dart and Flutter Basics (4), Testing, Performance and CI/CD (3). It has 3 easy, 23 medium, 4 hard questions, so you can start easy and work up to the harder ones.
Company type
Fintech
Headquarters
Bengaluru, India
Main India offices
Bengaluru, Pune
PhonePe Mobile App Development interview process
Online coding assessment
Machine coding round
DSA or problem solving round
Design or hiring manager round
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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01
How do you decide which devices to test on for an Indian user base?
Use analytics from the existing app or market data to identify the most common manufacturers, OS versions, screen sizes and RAM levels among your users. Cover a budget device with 3 to 4 GB RAM, a mid-range phone, a recent flagship, an older OS version you still support, and at least one iPhone and tablet. Use cloud device farms for wider coverage and add devices that generate many crashes.
02
A user reports that they cannot find your app in the store on their old phone. Why could this happen?
The app may not be available for their device because the minimum OS version is higher than theirs, the device lacks a required hardware feature declared in the manifest, the app is not released in their country, or the device architecture is excluded. Check the device catalogue in Play Console and the deployment target on iOS. Decide whether supporting that segment is worth lowering requirements.
Deep links open a specific screen in your app from a URL. Custom schemes like myapp://order/42 work but are not verified. Verified HTTPS links are App Links on Android, using assetlinks.json, and Universal Links on iOS, using an apple-app-site-association file on your domain. When verified, the link opens your app directly instead of the browser. The routing library, like go_router or React Navigation linking, maps URLs to screens.
04
A critical bug reaches production in a React Native app. How do you fix it quickly?
If the bug is in JavaScript, fix it, test on a preview channel, and publish an over-the-air update to production with a staged rollout, keeping it compatible with the current runtime version. If it needs native changes, build a hotfix release, submit it, and request expedited review on iOS if justified. Meanwhile disable the feature with a remote config flag if possible, and halt the store rollout.
05
How do you implement OTP login with a phone number?
The user enters a phone number, the backend or an auth service sends an OTP via SMS and returns a verification ID. The user enters the code, which is verified to issue session tokens. On Android, use the SMS Retriever or User Consent API to auto-read the code without SMS permissions; on iOS, set the text content type to one-time code for autofill. Rate-limit requests, expire codes quickly and protect against abuse.
06
What security practices should every mobile app follow?
Use HTTPS everywhere and consider certificate pinning for high-risk apps. Store tokens only in secure storage, never log sensitive data, and keep secrets on the server. Obfuscate release builds, validate all input on the server, and protect sensitive screens from screenshots where needed. Check device integrity with platform attestation APIs for high-risk actions, and follow the OWASP Mobile Application Security Verification Standard as a checklist.
Records are anonymous, immutable aggregates like (String, int) or ({String name, int age}), useful for returning multiple values without creating a class. Patterns let you destructure values and match shapes in switch expressions and if-case statements. Combined with sealed classes, switch can be exhaustive, so the compiler warns when a case is missing. They make state handling and parsing code shorter and safer.
08
Two users editing the same shared list offline create conflicting changes. How do you resolve conflicts?
Choose a strategy based on data. Last write wins, using server timestamps, is simple but can lose edits. Field-level merging keeps non-conflicting changes. For lists, treat each item as a separate record with its own version so edits rarely clash. For collaborative content, CRDT-based approaches merge automatically. Always let the server decide final order, and show users when their change was overwritten.
09
A Flutter screen shows a yellow and black overflow stripe on small phones. How do you fix it?
The overflow stripe means content exceeds the available space, often a Row with long text or a Column taller than the screen. Wrap text in Expanded or Flexible with overflow ellipsis, make the screen scrollable with SingleChildScrollView or a ListView, use LayoutBuilder to adapt for narrow widths, and avoid fixed heights. Also handle the keyboard by allowing the content to scroll when it opens.
10
What are over-the-air updates and what are their limits?
Over-the-air updates push new JavaScript bundles and assets to React Native apps without a store release, using services like EAS Update. They fix bugs quickly but can only change JavaScript and assets, not native code, permissions or SDK versions, which need a new build. Store policies allow them only if the app's core purpose does not change. Use runtime versions to ensure updates match compatible native builds, and roll out gradually.
Test business logic without widgets. For Bloc, the bloc_test package's blocTest builds the bloc with a fake repository, acts by adding events, and expects a list of emitted states. For Riverpod, create a ProviderContainer with overrides for repository providers, read the notifier, call methods and assert the state. Use mocktail for mocks and keep tests fast, deterministic and independent of the network.
12
A screen re-renders every time the user types in a search box, making it laggy. How do you fix it?
Keep the search text state local to the search input component so only it re-renders, debounce the query before updating the list or calling the API, and memoise the list and row components. Avoid storing frequently changing values in a global store that many components subscribe to. Use the React DevTools profiler to confirm which components render, and useDeferredValue to keep typing responsive.
13
What is hot reload and how is it different from hot restart?
Hot reload injects changed code into the running app and rebuilds the UI while keeping the current state, so you see changes in about a second. Hot restart reloads the whole app code and resets state, needed when changing initialisation logic, global variables or app startup. React Native offers Fast Refresh, similar to hot reload. Native code changes, such as new plugins or platform files, require a full rebuild.
14
How do you force users to update when an old version has a critical bug?
Keep a minimum supported version in remote config or an API endpoint, check it at startup and show a blocking update screen linking to the store. On Android, use the Play In-App Updates API with the immediate flow for critical updates and flexible flow for normal ones. Keep the backend compatible with older versions for a defined period, and use forced updates sparingly because they frustrate users.
15
Write a React Navigation setup with a stack containing a tab navigator and a details screen.
Create build flavours on Android and schemes or configurations on iOS, each with its own app ID suffix, app name, icon and API base URL, so all can be installed side by side. In Flutter, use --flavor with --dart-define-from-file for config values; in React Native, use react-native-config or Expo app config with environment variables. Keep secrets out of the repo and set them in CI.
17
Write a go_router configuration with an auth redirect.
Keys help Flutter match widgets to existing elements and state when the widget list changes. Without keys, Flutter matches by type and position, so reordering or removing items in a list of stateful widgets can attach state to the wrong item. Use ValueKey with a unique ID for list items, UniqueKey to force recreation, and GlobalKey rarely, for accessing state across the tree such as a Form.
19
How do you set up CI/CD for a cross-platform mobile app?
On every pull request, run lint, formatting checks, unit and widget or component tests. On merge, build signed Android and iOS release artifacts using CI services such as GitHub Actions, Codemagic, Bitrise or EAS Build, with signing keys stored as secrets. Use fastlane or EAS Submit to upload to internal testing tracks and TestFlight. Automate version numbers, generate release notes and run smoke tests with Maestro.
20
Your Flutter codebase mixes setState, Provider and get_it randomly across screens. How would you clean it up?
Agree on one approach with the team, for example Riverpod for app state and setState only for local widget state, and document examples. Migrate gradually, starting with the most buggy or most changed features, and write tests before moving logic. Add lint rules and pull request checklists so new code follows the standard. Avoid a big-bang rewrite that blocks feature work for weeks.
21
The client wants the app to look exactly like iOS on iPhones and like Material on Android. How do you approach this in a cross-platform app?
Identify which elements truly need platform-specific behaviour: navigation transitions, back gestures, date pickers, switches and dialogs. In Flutter, use adaptive constructors like Switch.adaptive or Cupertino widgets based on Theme.of(context).platform. In React Native, many components are native already, and Platform.select handles differences. Keep shared business logic and most layout common, and limit platform branches to a component library so they stay manageable.
22
How does the keyboard affect layouts in React Native and how do you handle it?
When the keyboard opens it can cover inputs, especially at the bottom of the screen. Use KeyboardAvoidingView with behavior padding on iOS, and rely on Android's adjustResize window setting, or use react-native-keyboard-controller for consistent behaviour on both. Wrap forms in a ScrollView with keyboardShouldPersistTaps set to handled so buttons work while the keyboard is open, and dismiss the keyboard on submit.
23
How do you design a mobile app for users on low-end devices and poor networks?
Keep the app size small, avoid heavy animations on low-end phones, and load images at the right resolution with caching. Use pagination and compressed API responses, cache data locally so screens open offline, and show skeleton loaders and clear retry options. Defer non-critical SDK initialisation to speed up startup. Test on budget devices with 2 or 3 GB RAM and throttled networks, since many users in India use them.
24
What is App Store Optimisation and what can a developer influence?
App Store Optimisation improves an app's visibility and conversion in store search. Key factors are the app title, subtitle or short description, keywords, long description, screenshots, preview videos, ratings and reviews. Developers influence it by keeping app size small, crash rates low and performance high, since store algorithms consider quality signals, by adding in-app review prompts at good moments, and by supporting localisation for regional languages.
25
After an API call finishes, the app throws an error about using BuildContext across async gaps or setState after dispose. How do you fix it?
The user left the screen before the Future completed, so the widget was unmounted. Before using context or calling setState after await, check if (!context.mounted) return; or if (!mounted) return; in State. Better still, move async logic out of widgets into a state management layer that the UI listens to, and cancel subscriptions or timers in dispose so no callbacks run on a dead widget.
26
Write a release checklist for a mobile app update.
1. Bump version name and build number on both platforms.
2. Run full automated tests and smoke tests on release builds.
3. Verify signing, obfuscation and debug symbol upload.
4. Check new permissions and update store privacy declarations.
5. Update release notes and screenshots if UI changed.
6. Upload to internal track and TestFlight; QA sign-off.
7. Submit for review with reviewer notes and demo account.
8. Start staged rollout at 5 to 10 percent.
9. Monitor crashes, ANRs, reviews and key metrics.
10. Expand rollout or halt and hotfix.
27
How would you plan a staged rollout for a major redesign?
Release to internal testers and beta users first and collect feedback. Then roll out to 5 percent of production users, monitoring crash-free rate, ANRs, key conversion metrics and reviews for a few days, before moving to 20, 50 and 100 percent. Keep the redesign behind a remote flag to switch back without a release. Define rollback criteria in advance and communicate the plan to support teams.
28
How do you secure Cloud Firestore data accessed directly from a mobile app?
Because the app talks to the database directly, security rules are the backend. Write rules that check request.auth for authentication and that users can read or write only their own documents, for example allow read, write: if request.auth.uid == userId. Validate fields and types in rules, never leave test mode rules open, and move sensitive operations like payments or role changes to Cloud Functions. Test rules with the emulator suite.
29
What are runtime permissions and how do they differ between platforms?
Both platforms require runtime approval for sensitive features like camera, location, contacts and notifications. Android requires declarations in AndroidManifest.xml and runtime requests for dangerous permissions; iOS requires usage description strings in Info.plist, and the app crashes if a description is missing when requesting. iOS allows asking only once; later the user must change settings. Plugins like permission_handler or react-native-permissions unify the API.
30
Deep links open the app but land on the home screen instead of the product page. How do you debug it?
Check that the link configuration maps the URL path to the right screen name, including nested navigators, and that path parameters match. Verify verified link setup on both platforms: assetlinks.json for Android and the associated domains entitlement plus the site association file for iOS. Test with adb shell am start and xcrun simctl openurl. Also handle links when the app is cold started versus already running.
Tips to crack the PhonePe Mobile App Development interview
Practise machine coding problems and focus on clean, extensible object-oriented design within the time limit.
Understand how UPI transactions work at scale, including idempotency, retries and reconciliation.
For analyst roles, prepare cases on transaction success rates, merchant adoption and fraud detection metrics.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; PhonePe interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the PhonePe Mobile App Development interview?
Candidates usually go through 5 stages: Online coding assessment; Machine coding round; DSA or problem solving round; Design or hiring manager round; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the PhonePe Mobile App Development interview?
This practice set leans on App Store and Play Store Publishing (7), Mobile Development Fundamentals (6), Dart and Flutter Basics (4), Testing, Performance and CI/CD (3). Revise those first, then practise explaining one or two of your own projects end to end, because most PhonePe interviewers ask you to walk through real work.
Are these the exact questions asked at PhonePe?
No. These are curated practice questions that match the skills and difficulty usually tested in fintech interviews like PhonePe's. They are not a leaked or verified list of past questions.
Where does PhonePe hire Mobile App Development professionals in India?
PhonePe has large teams in Bengaluru, Pune. Openings and locations change often, so check the PhonePe careers page and filter by city and experience.
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