Did the Adidas tech OA earlier this year for a backend role on their digital platform team. Wasn't sure what to expect so I went in mostly blind. Sharing this so nobody else has to.
Platform: HackerRank. Standard timed challenge.
Format: 2 coding problems, 90 minutes total. One SQL query question tagged on at the end (optional for my role but present).
Problem 1 was a medium-level array/string manipulation. Think sliding window or two-pointer territory. Solvable in 25-30 minutes if you've done any consistent LeetCode prep.
Problem 2 was harder. Graph traversal, BFS variant. Had to find shortest paths with some constraint that made a plain BFS insufficient. I got a working solution but it wasn't optimal and I'm pretty sure I missed an edge case. Still passed to the next round.
Difficulty calibration vs. FAANG: Easier than Google/Meta OAs. Closer to Amazon OA difficulty, maybe slightly below. If you've been doing LeetCode mediums consistently for a few weeks, you'll be fine. You probably don't need to crack hard problems unless you're going for a very senior-level role.
Time limit: 90 minutes felt sufficient. I finished with about 12 minutes left.
No system design in the OA. That comes later in the loop as a separate round.
One thing: the instructions didn't say which language was preferred, so I just used Python. No issues.
The SQL question was a multi-join aggregation, fairly standard. My guess is it's more relevant for data engineering or analytics roles.
Total timeline from OA invite to next-round scheduling: about 8 days. Not blazing fast but not glacial either.