Mobile Engineer
What the work looks like, the stacks behind the title, what each level means and the training that helps, then how interviews run and how to prepare for each step.
What a mobile engineer actually does
The apps people carry in their pocket, which have to stay fast, stable and simple on thousands of different devices.
A mobile engineer builds the apps a product offers on iOS and Android: the screens, the navigation, the data the app stores and syncs, and how it behaves offline or on a weak network. The code matters, and so do the choices around it: native or cross-platform, how the app talks to the backend and how it stays fast on older phones.
Mobile work also has its own rhythm. Each release goes through the App Store and the Play Store, so mobile engineers plan releases carefully, watch crash reports and work closely with designers, product managers and backend engineers.
More and more teams also work with AI coding tools such as Claude Code, Cursor or GitHub Copilot, and expect engineers to use them with judgment.
- Building a new screen or feature, and reviewing the code of other engineers
- A design review on a new flow with the product designer
- Agreeing an API contract with the backend team
- Preparing a release, or fixing a crash reported in production
- Time on performance, tests and technical debt
Many companies, from large tech groups to startups, hire their mobile engineers under the title Software Engineer, often followed by iOS or Android in brackets.
Behind the broader title, the platform and the stack described in the job ad show where the work really sits: native iOS, native Android or cross‑platform. On your CV and in interviews, describing the apps you shipped and their audience tells a company more than the title alone.
The same title, very different stacks
Most mobile searches are defined first by the platform and the framework of the team, then by the ground every mobile engineer shares.
What each level means in practice
Titles vary from one company to the next. What changes from one level to the next is the scope you own and the decisions you take.
- Builds well-defined screens with code review
- Learns the app, the tests and the release process
- Fixes bugs with support from the team
- Owns features from design to the stores
- Handles offline data and API calls
- Follows crash reports and fixes what they find
- Designs the architecture of the app for the team
- Leads technical decisions and their trade‑offs
- Mentors other engineers and owns release quality
- Sets mobile direction across several teams
- Owns shared modules, tooling and standards
- Writes the design documents others build on
The paths into the role, and what really counts
Companies look first at the apps you have built and shipped to the stores. Education and certifications help most early in a career, or to change field.
- Engineering school or master's in computer scienceThe most common path in France, and often expected by large companies.
- University degree in computer scienceThe most common path in the US, at bachelor's or master's level.
- Bootcamp or self-taught, with real projectsAccepted more often by startups, with an app published on a store to show.
- Moving from a nearby roleWeb and frontend developers often move to mobile, especially through React Native.
Our view: in mobile, an app on the store that you can walk through often says more than any certificate.
A conversation with a senior tech recruiter
Your first interview is with one of our senior tech recruiters, who knows the role, the stacks and the levels in this guide. The conversation covers your own work through real examples, and the technical exercises come later, with the company. Before the call, we send you the six themes we will cover so you can prepare your examples.
- What you owned yourselfThe apps, screens or features you were responsible for, and your own part in the team's work.
- Your environment and its constraintsNumber of users, devices and OS versions, legacy code, release rules or a small team: what shaped your technical choices.
- The decisions you madeNative or cross‑platform, an architecture or data choice, the options you compared and the reasons for the one you kept.
- The impact of your workWhat changed thanks to your work, with numbers when you have them: crash rate, store rating, app start time or usage.
- How you work with other teamsYour work with designers, product managers and backend engineers, and how you settle a disagreement.
- What you want nextThe kind of product, team and scope you are looking for in your next role.
- Apps in production and their audience
- Native or cross-platform choices
- Performance and stability
- Release quality
The same ground for every candidate. For a given role, every candidate answers the same final questions, built with the hiring manager around what the role really needs.
Ready for the next steps. After our call, we tell you how the company runs its interviews, who you will meet at each step and what each step is meant to assess.
What the company will assess, step by step
Each company runs its own process, and we walk you through its steps before you start. Mobile processes often combine the steps below, and the depth expected at each step grows with your level.
- A coding exerciseLive coding or a take-home on a realistic problem, such as a screen with a list, a call to an API and offline data.
- Mobile system designDesigning an app or a feature from a short brief: the architecture, the data, offline mode, sync and performance.
- A deep dive on your past workOne app you built, discussed in depth: its architecture, your choices, its crashes and what you would change today.
- Meeting the manager and the teamHow you work, how you take decisions with others and what the team expects in your first months.
- ConfirmedYou build a clean, working screen, explain each choice you make and follow the interviewer on the harder parts of the design.
- SeniorYou lead the discussion, go deep on two or three parts such as offline mode, sync or performance, and point out the limits of your own solution before you are asked.
- Staff and PrincipalYou run most of the interview as a peer, weigh the long-term consequences of each choice and connect the app to the backend, the releases and the other teams.
How to prepare as a mobile engineer
Practical advice for each step of a mobile process, from the way you introduce yourself to the questions you ask at the end of each interview.
Start with the apps you worked on, their audience and your part in them. Mention your stack in one sentence, then close with what you want next.
For each one, prepare the context, the constraints, your decision, the options you set aside, the result and what you would change today. Say "we" for the team and "I" for your own part.
Interviewers often ask about crash rate, store rating, app start time, number of users or release frequency. Orders of magnitude are enough, and they make your examples concrete.
In mobile system design, ask about the users, the network and what matters most before you draw anything. Then explain each choice with its trade‑off, and say where your design would reach its limits.
Keep to the time suggested and add a short README with your choices, their trade‑offs and what you would add with more time. A clean architecture, tests and a smooth screen count as much as the look.
Rules on AI coding assistants differ from one company to the next, and sometimes from one step to the next. Ask before each step, and when they are allowed, explain what you ask the tool and how you check its output.
- Walk us through an app you built: its architecture and the trade‑offs you made.
- How would the app behave offline, and how would it sync when the network comes back?
- Tell us about a crash in production, and what changed afterwards.
- How do you test your app and prepare a release?
- Native or cross-platform, and why did the team choose it?
- How often do you release, and who manages the stores?
- How do you follow crashes and app performance?
- How do designers and engineers work together on a new feature?
- How much time goes to technical debt?
- How does the team use AI coding tools day to day?
Where mobile engineers come from, and where they go
The roles people most often hold before this one, and the ones they most often move to.
Many mobile engineers also start as web developers, and some move to mobile tech lead roles.