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.” The rest of the author's notes on Software Engineer interview at The Trade Desk, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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