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Block new grad entry level interview: what I wish I knew before prepping

newgrad_neil · 4 replies

okay so i just finished my Block new grad interview loop for the SWE new grad role (cash app team) and i have a lot of feelings but mostly useful info. this is the post i was desperately looking for three weeks ago.

first: getting to the screen is the hard part. i applied twice before getting a response. what finally got me through was a referral from someone i met at a hackathon. if you don't have a connection, check linkedin and genuinely reach out, don't just spam the button.

OA (online assessment) two LC-style problems, 90 minutes. one was medium graph (BFS/DFS on a grid), one was medium-hard DP. i fumbled the DP a bit but passed. the bar feels like "can you finish at least one cleanly" rather than "ace both."

phone screen (45 min) one coding problem: medium-level linked list or array manipulation (mine was something about merging intervals). they also asked one behavioral: "tell me about a project where you had to learn something new quickly." don't skip behavioral prep even for an eng role at Block.

virtual onsite (4 rounds, all same day) coding 1: medium BFS problem, asked to trace through execution. they care about communication, not just the solution. coding 2: design a simple data structure (think something like a queue with min/max in O(1)). they pushed on space complexity. system design lite: for new grad level, this was more "design an API" than full distributed systems. something like: design the endpoints for a P2P payment flow, what would the request/response look like, how do you handle idempotency? behavioral: 3 questions, STAR format. "conflict with teammate", "time you failed", "why block/cash app specifically". the why-here question tripped a lot of people up. have a real answer.

they moved pretty fast in 2026 compared to what i read from 2024. got the debrief result in 4 business days.

i didn't get an offer (didn't pass the system design round i think) but going through the loop was genuinely instructive. prepping specifically for fintech payment concepts helped me sound more informed than i was.

4 replies

jp_newgrad

this is really helpful. what resources did you use for the system design lite prep? i'm a new grad too and all the usual resources feel way too senior-heavy.

newgrad_neil

alex xu's system design book has a section on payment systems that's actually new-grad friendly. also just reading through stripe's and cash app's engineering blog posts helped me understand idempotency and retry logic in a real context.

careerveteran

the "why block" question is not a gotcha, it's a signal filter. they get a lot of new grads who just need any offer. if you can't articulate why fintech and why cash app specifically, it reads as a lack of interest and that kills otherwise solid loops.

bootcamp_bri

wait the idempotency thing in the system design for payments, i totally blanked on that in a different fintech screen. can you say more about what a good answer looks like?