Unity Technologies Software Engineer
Interview Guide

Implement a binary search tree from an unsorted list and write a function to balance it.

Given an array of integers, find all unique triplets that sum to a target value.

Implement an efficient cache mechanism (such as LRU) with constant-time lookup and insertion.

Write a function to reverse a linked list both iteratively and recursively, explaining the memory trade-offs of each.

Explain the difference between value types and reference types in C#, and how they impact garbage collection.

How does the Unity Technologies garbage collector work, and what strategies can you use to prevent GC spikes in a high-performance application?

Describe the execution order of lifetime methods in a Unity script and how update loops are managed under the hood.

Explain how you would optimize a project experiencing low frame rates due to draw calls and CPU-to-GPU bottlenecks.

How would you structure a modular asset-loading pipeline that handles asynchronous downloads, caching, and local storage?

Describe a scenario where you had to work with a highly ambiguous requirement. What steps did you take to clarify the scope?

resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

Design an algorithm to detect cycles in a directed graph representing package dependencies.

What are shaders, and how does data flow from the CPU to the GPU through a graphics API pipeline?

Design a real-time multiplayer matchmaking system capable of handling hundreds of thousands of concurrent players.

Design an end-to-end auction system that supports real-time bidding with low latency and high consistency.

Explain how you would decouple a monolithic system into microservices, detailing how you would manage data consistency across boundaries.

Design a high-throughput telemetry ingestion service that collects performance metrics from millions of active client applications.

The egress service delivers about 1.5k webhooks/second across 40,000 destinations, with a per-destination concurrency cap of 4 and a 10-second connect-plus-read timeout. Throughput falls to 300/second, queue depth climbs, and p99 delivery latency for unaffected destinations goes from 200 ms to minutes, while the error rate barely moves. One tenant holds 900 destination rows whose URLs share a hostname that now answers in 9.5 seconds. Explain the mechanism with the arithmetic, then give the containment in the order you would apply it.