okay so I just finished the WBD online assessment and onsite coding rounds, wanted to share while it's fresh because I could not find good data on this before I went in.
online assessment (OA): platform: HackerRank. you get 90 minutes and 2 problems. no proctoring, timed only.
problem 1 was a two-pointer / sliding window problem on arrays. genuinely medium on leetcode by feel. i'd done probably 30 of these so it clicked fast.
problem 2 was harder, more like a graph BFS problem where you're traversing a grid and tracking visited states with a twist condition. i solved it but used more of my time budget than I wanted. no hard-level surprises though.
tip: read both problems before you start. the second problem I hit ended up being doable once I understood exactly what "visited" meant in their specific graph. spending 3 minutes reading carefully saved me 10 minutes of wrong approach.
onsite coding round (for the senior / mid-level loop, not new grad specifically): I'm a new grad so I only did the OA + one shorter coding round as part of a 3-round virtual onsite. the coding round was 60 minutes, one medium problem on hashmaps and one medium on trees. interviewer walked through my code live and asked me to optimize after I had a working solution. they wanted the big-O conversation, not just working code.
what surprised me: there was absolutely no SQL, no system design, no "implement a streaming algorithm" style problem. pure DS&A for the coding rounds. the behavioral round was totally separate.
also the interviewers were actually pretty human. one of them mentioned they've started flagging overly polished answers because they can't tell if a candidate actually solved it or memorized the pattern. so I'd recommend being transparent about your thought process even when you're stuck.
prep recommendation: if you're aiming for WBD SWE: leetcode mediums across arrays, hashmaps, trees, graphs, and BFS/DFS. 60-70 problems in those categories should cover you. no need to grind hards unless you're targeting staff level.
i'm still waiting on the decision. fingers crossed.