ByteDance interview notes, page 8 of 29

FAANG / Big Tech

Most of these ByteDance write-ups come from Software Engineers (194), then Machine Learning Engineers (45) and Data Scientists (17). The most reported rounds are the technical phone screen (227), the system design round (28), the behavioral / leadership round (16) and the onsite coding round (9).

289 interview notes · updated Sep 2026

ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SWE interview that came down to a classic cache design problem. Nothing too exotic but the O(1) constraint is where people trip up if they haven't thought it through before.

Design and implement an LRU cache with a fixed capacity that supports get and put operations in O(1) average time, evicting the least recently used entry when the cache is full.

“I knew the answer going in but still fumbled explaining why a doubly linked list specifically.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SWE interview with a parsing problem that looks straightforward until you actually have to handle edge cases. Stack-based approach, nested structures, the usual.

Given a string like '[1,[2,[3,4]],5]', parse it into the corresponding nested list structure.

“I knew pretty quickly it was a stack problem.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SET interview that was basically one giant test design question about WeChat QR-code payments. Way more scope than I expected for a single question, and I definitely underestimated how deep they wanted me to go on the security and concurrency angles.

Design a comprehensive test plan for a QR-code scan-to-pay feature. Your plan should cover happy paths, edge cases like insufficient balance or expired codes, network failures mid-transaction, security threats such as replay attacks and fraudulent codes, concurrency issues like double charges or double scans, idempotency, internationalization, accessibility, and performance. Organize it by functional, non-functional, and negative test categories.

“I started with the happy path and just kept going linearly, which was the wrong move.”

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ByteDance·Machine Learning Engineer·Technical Phone Screen

May 2026

Bytedance ML engineer interview that turned into more of a pure coding grind than I expected. They had me build the entire linked list scaffolding from scratch before even touching the actual problem, which ate up a chunk of time. Worth knowing if you're prepping for this loop.

Reverse the nodes of a linked list k at a time and return the modified list. Leftover nodes at the end (if fewer than k) stay in their original order. You cannot change node values, only relink the nodes themselves.

“Before I could even think about reversing anything, they asked me to write the node class, a helper to build a list from an array, and one to read it back.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance software engineer interview with a classic but brutal LFU cache design problem. The O(1) constraint is what makes it nasty, anyone can brute force it but they want the real thing.

Design and implement an LFU (Least Frequently Used) cache class with get and put operations, both running in O(1) average time. On eviction, remove the least frequently used key, and break ties by recency.

“The part I fumbled initially was the tie-breaking.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance software engineer phone screen, one coding question that was basically a sliding window variant. The interviewer seemed less sharp than expected, which honestly made the whole thing feel a bit anticlimactic.

You have a row of candies, each with a type. You can only collect two distinct types at a time, and once you pick a candy you must also take the one adjacent to it. If you hit a third type, you stop. Find the maximum number of candies you can collect.

“Classic sliding window once you see it, but the 'must take the adjacent one' constraint threw me for a second.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

First round for an SRE role at Bytedance. Pretty light technically, binary search on a sorted array, and there was enough time left over to just talk about the company with the interviewer.

Given a sorted array, find a target element using binary search.

“Not a LeetCode problem apparently, which I appreciated.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SWE interview with a graph/cycle detection problem. Pretty standard stuff for a tech company at this level but the edge cases they expected you to catch were more specific than I anticipated.

Given a number of courses and a list of prerequisite pairs, determine whether it's possible to complete all courses without running into a circular dependency.

“I went straight to topological sort via BFS and it worked, but I fumbled on the self-loop case for an embarrassingly long time.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SWE interview threw a classic hard algorithm problem at me. The histogram rectangle question is one of those problems where you either know the trick or you're cooked.

Given an array of integers representing the heights of histogram bars (each of unit width), find the area of the largest rectangle that can be formed within the histogram.

“You need a monotonic increasing stack of indices.”

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ByteDance·Software Engineer·Technical Phone Screen

May 2026

Bytedance SWE interview that went deep on LRU cache design, then kept pushing further into TTL extensions and thread-safety. More of a design conversation than a pure coding session, which I wasn't fully expecting.

Implement an LRU cache with O(1) get and put operations. Walk through your data structure choices.
How would you handle eviction when the cache exceeds its capacity?
Extend the cache to support per-entry TTL. What are your options for expiring entries?
What are the trade-offs between lazy expiration and active expiry with a background process?
How would you make this cache thread-safe?

“Started with the hashmap plus doubly linked list combo which is the obvious answer, but they made me actually justify why a singly linked list wouldn't work.”

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