Three loops at State Street in the last two years (different roles, one offer, two rejections). Here's what I've learned about how their coding interviews actually work.
Online assessment
HackerRank platform, two problems, 90 minutes. The difficulty consistently sits at what I'd call "comfortable medium" to "medium that requires you to think for a bit." I've seen: Hash map / two-pointer problems String manipulation with multiple edge cases One graph problem (BFS, fairly standard)
They're not looking for DP trick shots. They want to see clean correct code and they do run hidden test cases, so edge cases matter. I've heard from someone who scored perfectly on the OA and still didn't pass because the hidden tests included null inputs they didn't handle.
Language: Java and Python are the most natural fits given their stack, but I've done it in Java and seen others use Go. Pick what you're fastest in.
Live coding rounds (phone screen and onsite)
These are timed 30-45 minutes, one interviewer, collaborative. The interviewer generally tells you upfront whether they want you to code or talk through the approach first. I always ask even if they don't volunteer it.
Once you get to the onsite, the live coding round can spike difficulty. My hardest problem was something involving interval merging with some finance-flavored context ("positions within a time window" type framing). It was a medium but the framing added noise. Stripping the domain language out of the problem first helped.
Things I wish I knew: They do ask you to test your own code. Not just "does this look right" but "walk me through a test case." If you're not used to doing that out loud, practice it. The behavioral questions are woven into coding rounds too, not just their own separate block. Expect "tell me about a time you had to optimize something under a deadline" after you finish a problem. They're a Java shop in a lot of places. If you're a Python person prepping generically, spend time making your Python readable and adding type hints. One interviewer commented positively on my type annotations unprompted.
Overall difficulty relative to other fintech: similar to Fidelity, easier than Two Sigma or Citadel. The bar is real but approachable with solid medium-level prep.