How to become a quant
« Quant » names four different jobs. Picking which one you are applying for is the first real decision, because the interviews barely overlap.
Four jobs, one word
A quant trader prices and takes risk in real time; the interview is mental arithmetic, expected value and market making games. A quant researcher looks for signal in data; the interview is statistics, inference and whether your idea survives out of sample. A quant developer builds the systems that carry the orders; the interview is C++, concurrency and design. A hardware engineer puts the hot path in silicon; the interview is RTL, timing and clock domains.
All four share one screen at the front: probability and arithmetic under time pressure. That is why it is the thing worth building first, whichever seat you end up in.
What actually gets you filtered out
Rarely the mathematics. Far more often: going silent while you think, giving a point estimate with no sense of how wrong it might be, and folding the moment an interviewer says « are you sure? » — which they will say when you are right, precisely to see what you do.
Do I need to have traded before?
No. Graduate and internship pipelines assume none. What they assume is that you can think about uncertainty out loud, and that is trainable.
Which track should I pick?
The one matching what you already do well. Firms hire depth, not coverage — a strong developer who also quotes badly loses to a strong developer.