Hadrian Software Engineer Interview Experience — Three Rounds Ending in an On-site Factory Tour and a DAG Critical-Path Problem

Applied online and a recruiter reached out. Their process is like this:

1. Round 1
   • 1 hr live coding phone screen
2. Round 2
   • 45-min leadership/behavioral with an engineering director
   • 60-min system design
3. Round 3
   • On-site in Torrance with a factory tour
   • 30-min "partnership" interview (working with non-technical stakeholders)
   • 1 hr coding

Problem: A work order is modeled as a DAG. Nodes are operations (machining, inspection, and so on), each with a duration in days, and edges are dependencies. All paths end at a terminal "shipping" node. Compute the total lead time, meaning the critical path length: the longest path from any starting node (no incoming edges) to shipping.

Input was a list of nodes (id, type, duration) and a list of edges (source, target).

Similar to LeetCode's Parallel Courses III.

I passed.