The Trade Desk interview notes, page 1 of 2

Large Enterprises

Most of these The Trade Desk write-ups come from Software Engineers (16), then Data Scientists (3) and Machine Learning Engineers (1). The most reported rounds are the technical phone screen (12), the system design round (4), the onsite coding round (3) and the behavioral / leadership round (1).

20 interview notes · updated Jul 2026

The Trade Desk·Software Engineer·Onsite - Coding / Algorithms

Apr 2026

Tradedesk SWE interview had a file system coding problem that looked manageable on the surface but had enough edge cases to keep you honest.

Implement two functions: one that compresses a file (appends a '.COMPRESSED' suffix and halves its size, but only if the caller owns the file), and one that decompresses it (strips the suffix and doubles the size, but must check for filename collisions and whether there's enough capacity first).

“The ownership check on compress was fine, that part clicked fast.”

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The Trade Desk·Software Engineer·Technical Phone Screen

Apr 2026

Interviewed for a SWE role at The Trade Desk and got a system design question about extending an LRU cache with a custom eviction policy. Pretty niche problem, felt like it was testing whether you actually understood the internals rather than just knowing the textbook definition.

Design a custom policy extension for an LRU Cache. How would you modify or extend the standard implementation to support pluggable or configurable eviction strategies?

“My first instinct was to just describe a doubly linked list plus hashmap setup, which is the standard answer, but that wasn't really the point.”

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The Trade Desk·Software Engineer·Onsite - Coding / Algorithms

May 2026

Coding round for a software engineer role at Tradedesk. The question was a bowling score calculator, and I fumbled it pretty badly since it wasn't the typical LeetCode format I'd been grinding.

Implement a bowling score calculator. You define your own input format and must handle all the scoring rules, including strikes (where the next two balls are added to the 10), and the special case of the 10th frame allowing up to three balls.

“This was not a clean algorithmic puzzle with a neat answer.”

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The Trade Desk·Data Scientist·Technical Phone Screen

May 2026

Technical screen at Tradedesk for a DS role, basically one big system design question about deploying a new CVR model in a live RTB environment. The question had a lot of moving parts and I don't think I covered all of them cleanly.

You've built a new CVR prediction model for an RTB bidding system and offline metrics look better, but how would you design an online evaluation and rollout plan to confirm it actually improves business outcomes in a live auction environment?

“This is a monster of a question and I underestimated how interconnected all the pieces are.”

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The Trade Desk·Software Engineer·Technical Phone Screen

May 2026

Tradedesk software engineer interview was basically one big OOP design problem split across four levels, each one building on the last. The problem itself was clean and well-scoped, but four levels is a lot to get through cleanly under pressure.

Design and implement an in-memory cloud storage system starting with basic file operations: adding a file, copying a file, and retrieving a file's size.
Extend the storage system with a file search feature that filters by prefix and suffix, returning results sorted by size descending and then lexicographically ascending for ties, formatted as name(size).
Add a user and capacity system to the storage system, including adding files on behalf of users, updating a user's capacity with automatic file removal, and updating copy_file to enforce ownership and capacity constraints.
Add compress and decompress operations to the storage system, where compression halves the file size (floor division) and renames the file with a .COMPRESSED suffix, and decompression reverses this while checking capacity constraints.

“The first level felt almost too easy.”

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The Trade Desk·Software Engineer·Technical Phone Screen

May 2026

Phone screen for a software engineer role at Tradedesk. The coding problem was a 3Sum variant with a longer problem statement, and I kind of tripped over myself by not reading it carefully enough before jumping in.

Given an array of integers, find all unique triplets that satisfy a specific set of conditions (a variant of the classic 3Sum problem with additional constraints described in a longer problem statement).

“Skimmed the problem and missed some of the conditions buried in the description.”

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The Trade Desk·Software Engineer·Technical Phone Screen

May 2026

Coding round at Tradedesk with a file search problem that looks straightforward but has a few sorting gotchas worth thinking through carefully.

Implement a function called find_file that searches for files matching a given prefix and suffix, then returns them sorted by size descending and name ascending, formatted as 'name(size)'.

“The filtering part was fine but I tripped up on the sort.”

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The Trade Desk·Software Engineer·Technical Phone Screen

May 2026

Did a coding round for a Software Engineer role at Tradedesk that was basically a cloud storage simulation problem. Pretty straightforward Level 1 stuff but the edge cases in the spec are where things get interesting.

Design and implement a basic cloud storage system with three operations: adding a file (should return false if the file already exists), copying a file (should fail if the source doesn't exist or the destination already exists), and retrieving a file's size (should return null/None if the file isn't found).

“The add and get_file_size parts were pretty quick to knock out.”

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The Trade Desk·Software Engineer·Onsite - System Design / Architecture

May 2026

System design round at Tradedesk that skipped the usual 'design a social network from scratch' format and instead walked through a scenario incrementally, eventually landing on a read-heavy architecture problem where precomputation was the key lever. Felt more like a conversation than a quiz, which I wasn't totally prepared for.

Design a system optimized for a read-heavy workload (think something like a social feed), and walk through how you'd handle scale using precomputation strategies.

“The question evolved gradually so I didn't realize we were heading toward precomputation until we were already knee-deep.”

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The Trade Desk·Software Engineer·Technical Phone Screen

Jun 2026

Tradedesk software engineer interview that centered on a recipe management system design problem. The core challenge was extending a basic CRUD system with search, and the real meat was justifying your data structure choices under pressure.

You have a Recipe Management System with add, update, and delete operations. How would you implement a search_by_ingredient function, and what are the trade-offs between a naive scan and maintaining an inverted index?

“I went straight for the inverted index because it felt like the obvious answer, but then they pushed back and asked me to actually quantify the cost difference.”

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