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Google iOS interview

Google's process leans on general software engineering rigor, with iOS specifics layered on. Knowing the balance tells you how to split your prep.

What to expect

Expect a strong emphasis on data structures, algorithms, and clean problem solving, since Google's coding bar is largely language-agnostic, plus system design at senior levels and behavioral rounds around Googleyness and leadership. iOS-specific depth still matters for role fit, but the coding rounds resemble general SWE more than platform trivia.

How to prepare

Invest in algorithmic problem solving and complexity analysis, practice communicating a clean solution, and prepare system design including mobile-flavored scenarios. Keep your iOS fundamentals sharp for role-specific discussion. Balancing general coding strength with iOS depth is the right preparation for Google.

What the coding rounds actually score

Having conducted more than 500 mobile interviews and calibrated against loops like this one, I can tell you the score in an algorithm-heavy round is not the algorithm. It is the process around it. Interviewers write feedback on whether you clarified inputs and constraints before coding, whether you stated a brute force and named its complexity before optimizing, whether you tested your own code against edge cases without being told, and whether a hint moved you forward or bounced off. Two candidates can produce the same working solution and receive opposite recommendations, because one of them walked through the reasoning and the other just arrived. This is good news for iOS engineers worried about the language-agnostic bar. The process is trainable, it transfers directly from careful engineering habits you already have, and it is worth more than memorizing a longer list of problems. Correct answers are the entry fee. Reasoning under pushback is the score.

Spoken patterns for the algorithm round

The strongest candidates run a spoken loop you can rehearse word for word. Restate the problem and confirm it: "So I get an unsorted array and need the k largest, and duplicates count separately, right?" Name the naive answer and its cost before improving it: "Sorting gives me n log n, but a heap of size k gets this to n log k." Announce your plan in two sentences before typing. While coding, surface only decisions, not syntax. When done, do not say "done". Say "let me test this", and walk one normal case and two edge cases out loud. This last step alone separates candidates, because most stop at the moment their code looks right. In Swift, know the costs of what you reach for: what sorting costs, what dictionary lookups cost, when a value type copy matters. The interviewer may not write iOS code, but they will notice whether you understand your own tools.

Traps and recovery when you stall

The classic trap in this kind of round is silent optimization: the candidate sees the brute force, decides it is beneath them, and goes quiet hunting for the clever answer. Five minutes of silence later, they have nothing on screen and the interviewer has nothing to score. Say the brute force. It is not a confession, it is a floor, and interviewers routinely mark candidates up for establishing it and improving from there. The second trap is fighting a hint. Interviewers in structured processes give hints on purpose and score what you do with them. Take the hint, run with it visibly, and say what changed: "Right, if I sort first then the pairs become adjacent, let me redo this." When you are stuck outright, the recovery line is to narrow the problem out loud: "Let me solve it for a sorted input first and then remove that assumption." Progress you can see beats a perfect answer that never arrives.

Mobile system design for a general audience

At senior levels expect a design round, and for a mobile role expect mobile-flavored scenarios: design a photo feed, an offline-first sync layer, a chat client. The trap here is inverted. Your interviewer may be a strong generalist rather than a mobile specialist, so unexplained platform jargon reads as hand-waving rather than depth. Translate as you go: do not say "I would use background tasks", say "the OS can terminate us at any point, so every sync step must be resumable, and here is how I checkpoint it". Anchor the design in the constraints that make mobile different: unreliable networks, limited battery, app lifecycle, and a client you cannot patch instantly because releases go through review and users update slowly. Naming those constraints unprompted, then designing around them, is the clearest senior signal available in this round, and it works no matter who is on the other side of the call.

How to split your preparation time

Split by scarcity, not comfort. Most working iOS engineers are weakest on timed algorithmic problem solving, so that gets the bulk of the calendar: regular timed sessions, out loud, with the spoken loop above, until the process runs on autopilot under pressure. Reserve a steady slice for mobile system design, practicing two or three scenarios end to end rather than skimming ten. Keep iOS fundamentals warm with brief reviews, since for an experienced engineer that knowledge needs refreshing, not rebuilding. And rehearse behavioral stories with concrete outcomes, because structured loops weigh them more than candidates assume. The common failure is spending prep time polishing existing strengths because it feels productive. The loop will find the weakest round, so your preparation should go there first.