reddit iOS Engineer Interview: Questions, Experience & Prep (2026)

Reddit is one of the largest social platforms in the world, and its iOS app is a critical part of how hundreds of millions of users browse communities, vote on posts, and connect with each other. An iOS Engineer at Reddit typically works on the core consumer app, touching areas like feed rendering, real-time updates, community tooling, and media playback.

As of July 2026, knok's job radar shows 70 iOS Engineer openings across India. Delhi leads with 21 roles, followed by Bangalore (6), Mumbai (3), and Chennai (2). Reddit currently lists 208 open roles across all functions globally, signalling active hiring. Hyderabad and Pune show no iOS openings in the current data.

The interview process at Reddit typically spans four to five stages. Candidates report a recruiter screen, a technical phone screen focused on Swift and iOS fundamentals, one or two coding rounds, a system design round, and a set of behavioural interviews. The exact structure can vary by team and level, so confirm with your recruiter. Reddit places strong emphasis on product thinking, so expect questions about how you would actually improve the Reddit app, not just how you write code.

For compensation, Glassdoor and levels.fyi have publicly reported figures from Reddit employees at various experience levels. Check those platforms before your negotiation conversation.

These questions are based on patterns candidates report for Reddit iOS Engineer interviews. Your actual interview will likely cover a mix of technical depth, system design, and product thinking.

1. Walk me through how you would redesign the Reddit home feed to improve scroll performance on older iPhones.
2. How have you optimised a UITableView or UICollectionView that renders heavy media such as images and video thumbnails?
3. Reddit supports many subreddits with very different content types. How would you build a reusable, modular UI component system to handle this variety?
4. How would you implement offline reading so users can browse their Reddit feed without a network connection?
5. Reddit shows vote counts that update in near real time. How would you design the client-side architecture to keep the UI in sync without overloading the server?
6. Describe a production crash you debugged that only reproduced on a specific iOS version or device. How did you find the root cause?
7. Tell me about a feature you shipped that had a clear, measurable impact on user engagement or retention.
8. How do you manage memory in a feed app that renders hundreds of images and videos as the user scrolls?
9. Walk me through your approach to testing iOS code. What kinds of tests do you write, and where do you draw the line on coverage?
10. How would you migrate a large legacy Objective-C codebase to Swift incrementally without disrupting ongoing feature work?
11. Reddit communities can have unique layouts and custom widgets. How would you architect a plugin or feature-flag system to support this at scale?
12. Describe a time you pushed back on a product or design requirement because of a genuine technical constraint. What happened, and what was the outcome?

Use STAR for every behavioural and product question: keep Situation and Task brief, spend most of your answer on Action, and end with a concrete Result.

Q: How have you optimised scroll performance in a feed with heavy media?

*Situation:* At my previous company, our content feed displayed images, embedded videos, and polls in every cell. On mid-range iPhones the scroll frame rate would drop noticeably during fast scrolls.

*Task:* I owned the performance sprint and needed to restore smooth scrolling without removing any content types from the feed.

*Action:* I profiled the app with Instruments and found two main bottlenecks. Image decoding was happening on the main thread, so I moved all decoding to a background DispatchQueue and introduced a pre-decoded image cache keyed by URL. Auto-layout constraints were also being resolved on every scroll event for the most complex cells, so I rewrote those cells to use manual layout in layoutSubviews and cached the calculated heights.

*Result:* Scrolling became visibly smooth on newer iPhones and noticeably better on older devices. Internal session-length data showed users were scrolling further per session, though the exact lift was a small-sample observation from our analytics dashboard.

Q: Tell me about a time you pushed back on a product requirement.

*Situation:* The product team wanted to add full-screen video autoplay that would start the moment a post entered the viewport, similar to short-video apps.

*Task:* I was the iOS lead for this feature and had to evaluate whether it was technically feasible within acceptable battery and memory limits.

*Action:* I built a quick prototype and measured CPU and battery draw with Instruments. The results showed significant drain, especially on devices with less RAM. I wrote a short technical brief summarising the findings, proposed a constrained alternative (autoplay only the topmost visible post and pause all others), and presented both options with data at our next weekly sync with the PM and designer.

*Result:* The team agreed to ship the constrained version. Battery impact stayed within our target range, the PM confirmed the core user experience goal was still met, and the feature shipped on schedule.

Q: Describe a feature you shipped that had a measurable impact.

*Situation:* In our app, tapping a notification took users to a generic feed page rather than to the specific post or comment they were notified about.

*Task:* I was asked to fix the deep-linking logic so that every notification type landed users on the correct piece of content.

*Action:* I audited all notification payload types, built a universal link router that parsed each format, and added fallback logic for expired or deleted content. I also wrote integration tests covering each notification category to prevent regressions in future.

*Result:* After the fix shipped, our product team noted a clear improvement in notification-driven session starts in our internal analytics. Because this was an internal measurement I cannot cite a public figure, but the improvement was visible in the dashboard within the first week after launch.

For technical depth questions (memory management, scroll performance, architecture choices): structure your answer as Diagnosis, Decision, Trade-offs. First explain how you would identify the problem, for example using Instruments, the Xcode memory graph, or structured logging. Then describe the solution you chose. Then name one alternative you considered and why you ruled it out. Reddit interviewers want to see engineering judgment, not just a recitation of the right answer.

For system design questions (feed architecture, offline support, real-time updates): work top-down. Start with the user need, then the data model, then the networking layer, then the caching strategy, then edge cases. Explicitly call out iOS-specific constraints such as background fetch limits, push notification quotas, and App Store review requirements. Interviewers appreciate candidates who connect the design to real behaviour visible in the Reddit app today.

For behavioural questions: use STAR cleanly. Keep Situation and Task to one or two sentences each. Spend the bulk of your answer on Action, because that is where your judgment shows. End Result with a real metric if you have one. If you do not have a precise number, describe the qualitative outcome and what you learned. Invented numbers are easy for experienced interviewers to probe.

For product thinking questions (how would you improve the Reddit iOS app): use a three-part structure. Identify the user problem. Propose a solution with iOS-specific details such as gestures, home-screen widgets, or notification types. Explain how you would measure success. Bonus: reference a specific Reddit behaviour you have observed as a user, such as the vote animation or the awards system, to show you genuinely use the product.

Product ownership, not just code. Reddit interviewers look for engineers who think about why a feature exists, not only how to build it. Connecting your past technical work to user outcomes is one of the clearest ways to stand out.

Swift fluency and UIKit or SwiftUI depth. Expect questions on concurrency (async/await and actors), memory management (ARC, weak vs unowned references, and common retain cycle patterns), and rendering pipelines. Because Reddit's app has a long history, you may also be asked about bridging Objective-C and Swift in a single project.

Performance instincts. The Reddit feed handles enormous variety: text posts, image carousels, embedded video, polls, and community awards. Interviewers want to see that you have a practised eye for scroll jank, memory pressure, and battery drain, and that you reach for Instruments before guessing at a fix.

Collaborative communication. Reddit runs small, cross-functional teams. Candidates report that behavioural rounds focus on how you handle disagreement with product managers, how you give and receive code review feedback, and how you support engineers who are less experienced than you.

Genuine curiosity about Reddit. Use the app before your interview. Know the major surfaces: home feed, community pages, post detail, chat, and notifications. Interviewers consistently notice when a candidate has clearly not used the product they are interviewing for.

A focused four-week plan for a Reddit iOS Engineer interview.

Before each round, re-read the job description and map your stories to the requirements listed. Candidates report that Reddit interviews often open with 'tell me about a project you are proud of', so have your strongest story ready in under two minutes.

On the day, confirm the interview format with your recruiter. Candidates report that coding rounds use a shared online editor, so practise typing code without IDE autocomplete before the interview.

While you are preparing, knok checks 150+ job sites nightly, applies to roles that match your resume, and messages HR for you, so you do not miss a new iOS opening while you are focused on studying.

Skipping the 'why' in architecture answers. Many candidates describe what they built but never explain the trade-offs they weighed. Reddit interviewers probe for this, so always name at least one alternative you considered and why you ruled it out.

Underestimating behavioural rounds. The Reddit interview process typically weights behavioural signals heavily alongside technical ability. Candidates who over-prepare on coding but under-prepare on collaboration stories often struggle in the later rounds.

Treating UIKit and SwiftUI as separate worlds. Reddit's iOS codebase spans many years, so you are expected to be fluent in UIKit and to have working knowledge of SwiftUI, including how to use both in the same project. Mentioning only one framework signals a gap.

Not knowing the product. Candidates report being asked directly how they would improve Reddit's iOS app. Saying you do not really use Reddit is a significant red flag in a consumer product company interview.

Inventing metrics. If you do not have a precise number for a result, be honest and describe the qualitative outcome instead. Fabricated figures are easy for experienced interviewers to probe and they almost always backfire.

Ignoring edge cases in system design. Reddit handles a huge variety of communities and content types. In system design rounds, proactively mention how your design handles deleted content, banned subreddits, slow or offline networks, and accessibility requirements.