I went through the Bloomberg loop twice. First time was pretty blind. Second time I got the offer. Here's the actual preparation I'd do from day one if I could restart.
Coding prep: Bloomberg uses a mix of easy-to-medium and medium-to-hard LeetCode-style problems but with a preference for problems that have a financial or data-stream flavor. Graph traversal, heaps, sliding window, order book logic, anything involving time-sequenced data. If you're looking for specific practice, think: design a stock ticker feed, find the median of a streaming data set, validate a trade log for anomalies. Not random DP problems.
They use Pair interview platform or code-in-Google-Docs depending on who you're talking to. Ask your recruiter so you're not surprised.
Systems design: This is where I underinvested first time. Bloomberg cares specifically about: Low-latency data pipelines (financial data, not just web traffic) Message queuing and guaranteed delivery (they live and die by data accuracy) Designing for reliability and failover, not just scale
If you've never worked in financial infrastructure, read up on what makes it different from typical web-scale design. Grokking System Design is fine as a base but won't get you there alone.
Behavioral prep: They ask a lot about times you had to deal with production incidents, high-stakes deadlines, and client-facing errors. The theme is accountability under pressure. Prepare 2-3 STAR stories specifically for these. Generic 'led a project' stories aren't as strong as 'the system went down at 9:30am on a trading day and here's what I did.'
C++ expectation: You don't need to be a C++ wizard but you should be able to read and reason about it. They'll mention C++ in the JD and mean it. Know the basics of memory management, know why performance matters in this context.
Homework: Spend 2 hours on the Bloomberg Terminal product before your loop. You should be able to explain why a fixed-income trader would use Bloomberg instead of alternatives. Even for SWE roles this context shows up in how you think about the work you'd be doing.
Time to competent is longer than most companies. Go in knowing that.