Moloco Software Engineer interview questions

13 Software Engineers have shared notes from their Moloco interviews, with the questions they were asked in each round. That is 72% of the 18 Moloco interview notes on Screna AI.

13 Software Engineer interview notes

Moloco·Software Engineer·Onsite - System Design / Architecture

Jul 2026
System design round at Molocoads for a software engineer role, centered entirely on building an autocomplete service at scale. Pretty deep dive, they wanted opinions on everything from cache layers to update pipelines, not just a high-level sketch.
  • Design a large-scale autocomplete service that returns the top 5 query suggestions within 100ms as a user types, ranked by popularity and recent trends.
  • How would you design the API for an autocomplete service, and what does the data model look like underneath it?
  • How would you handle sharding and hot prefixes in a high-traffic autocomplete system?
  • Walk through your cache design for this system, including what you cache, at what layer, and how you handle invalidation.
  • Describe the offline and online pipelines you'd build to keep autocomplete suggestions fresh and updated from new search logs.

“This is a meaty one and I underestimated how many sub-problems were hiding inside it.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
Did a coding round for a Software Engineer role at Molocoads with two algorithm problems. Nothing too wild, but the second one had me second-guessing my approach the whole time.
  • Given a list of rooms where each room contains keys to other rooms, determine whether you can visit all rooms starting from room 0.
  • Given a balanced parentheses string, compute its score using the rules: "()" = 1, concatenation adds scores, and wrapping a string in parens doubles its score.

“Graph traversal problem basically.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
Interviewed for a software engineer role at Molocoads and got a range-sum problem that started simple and then got progressively harder. The follow-up about making it mutable is where things got interesting and I felt a bit underprepared for the full tradeoffs discussion.
  • Design a data structure that supports efficient range sum queries on an integer array, first for an immutable array, then extended to support point updates as well. Both operations should scale to arrays and query counts in the hundreds of thousands.

“Part one was fine, prefix sums, done in two minutes.”

View Post

Moloco·Software Engineer·Onsite - System Design / Architecture

Jun 2026
System design round at Molocoads for a software engineer role, centered entirely on building a search autocomplete system at Google scale. Pretty deep dive, lots of follow-ups on the data pipeline and serving layer.
  • Design a search autocomplete (typeahead) system that can handle billions of queries per day, returning the top-K completions for a given prefix ranked by popularity, with sub-100ms latency at p99.
  • How would you handle real-time trending queries in the autocomplete system without blowing up your serving infrastructure?
  • Walk me through how you'd shard and replicate the serving layer, and what happens when a shard goes down.
  • How would you incorporate personalization, locale handling, and safety filtering (e.g. suppressing illegal or harmful completions) into the system?

“This is one of those questions where you think you know it cold and then the follow-ups expose every gap.”

View Post

Moloco·Software Engineer·Onsite - System Design / Architecture

Jun 2026
Round 2 at Molocoads for a software engineering role, system design with a Korean interviewer who was pretty chill. Just the one question but it had some depth to it.
  • Design a real-time comment system similar to Facebook's.

“This is one of those questions where you think you know where to start and then realize halfway through that the 'real-time' part is doing a lot of heavy lifting.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
Interviewed for a software engineer role at Molocoads and got hit with a pretty involved array problem that had a follow-up I was not expecting. The core question was manageable but the circular variant threw me off a bit.
  • Given an integer array, for each index i, find the maximum length of a contiguous subarray that contains i and whose maximum element is exactly nums[i].
  • Follow-up: how would you modify your solution if the array is circular, meaning the subarray can wrap around from the end back to the beginning?

“The key insight is that you're basically looking for how far left and right you can walk from i before hitting something strictly larger.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
One round with a senior Korean interviewer who was genuinely pleasant despite a thick accent making some back-and-forth a bit tricky. The technical problem was deceptively simple on the surface but turned into a pretty long conversation about optimization.
  • You have a log file where each entry is a (user, ad-click) pair and a single user can appear many times. How do you compute the total number of clicks per user, and how do you optimize beyond a naive O(n) worst case?

“Started with the obvious grouping approach and the interviewer nodded along, then asked how to make the worst case better.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
Interviewed for a software engineer role at Molocoads and got a graph traversal problem about unlocking rooms. Pretty standard algorithmic question but it's the kind that trips you up if you overthink the setup.
  • You have n rooms labeled 0 to n-1, all locked except room 0. Each room contains keys to other rooms. Starting from room 0, can you visit every room? Given the list of keys per room, return true or false.

“Classic graph reachability problem.”

View Post

Moloco·Software Engineer·Technical Phone Screen

Jun 2026
Molocoads coding round, one problem the whole time. Grid simulation with bubble elimination and gravity. Nothing flashy, just had to get the mechanics right without tripping over edge cases.
  • Given a 2D grid of colored bubbles, identify and eliminate groups of adjacent same-color cells that meet a size threshold, then apply gravity so remaining cells fall down and empty cells rise to the top. Return the resulting grid.

“The problem itself isn't hard conceptually but I kept second-guessing my BFS for the grouping step.”

View Post

Moloco·Software Engineer·Technical Phone Screen

May 2026
Did a coding round for a Software Engineer role at Molocoads. The problem looked deceptively simple at first glance but the follow-ups pushed into binary search territory which I wasn't fully prepared for.
  • You're given a sorted array where every value appears exactly k times in a row, except for one value that appears exactly once. Write a function to find and return that unique value.
  • What is the relationship between the array length n, the repetition count k, and the number of distinct repeated elements? Express n as a formula.
  • Can you redesign your solution to run in O(log n) time using binary search, taking advantage of the sorted grouping structure?

“My first instinct was a hash map and I almost said it out loud before catching myself.”

View Post