Moving from a service company to a product company means a different loop and a different story. Practise both.
The gap between service and product company loops is rarely raw intelligence. It is that service company work is organised around delivering to a specification, while product company interviews are organised around decisions you made. Both the technical and behavioral rounds are calibrated on that difference.
On the technical side the obvious gap is DSA depth. Product loops expect fluency at medium difficulty with optimal solutions reached inside the round, plus a machine coding or design round that assumes you have opinions about class structure. On the behavioral side, the harder gap is narrative: "we delivered what the client asked for" is a delivery story, and interviewers hear it as an absence of ownership.
The fix for the narrative half is not invention. Most service-company engineers have made real technical decisions - a performance fix, a design they pushed back on, an integration they owned - and have simply never framed them as decisions. Practising that reframing out loud is worth as much as another hundred coding problems.
60-90 min
Timed DSA. Often the first hard filter and where most transitions stall.
45-60 min
Medium to hard problems with the optimal solution expected inside the round.
60-90 min
Working code with clean class boundaries, then extended under a new requirement.
60 min
Introduced from SDE-2 upward. Trade-offs, not component lists.
45 min
Ownership and decisions. The round where service-company framing costs the most.
For most engineers, three to six months of consistent preparation. The DSA bar is the slow part; the design and behavioral reframing move faster once you start practising them out loud rather than reading about them.
Reframe delivery as decisions. Instead of "we built what the client specified", find the moments you chose something - a schema, a performance fix, a design you argued against - and tell those with the constraint, your call, and the outcome. The work is usually there; the framing is what is missing.
The online assessment. It is purely DSA, strictly timed and unforgiving of partial solutions, so it filters before anyone evaluates your experience. That is where preparation should start.
Start with the DSA bar, then practise telling your work as decisions rather than deliveries.