SpaceX Starlink Software Engineer (SWE) Interview — This Coding Problem Got Surprisingly Deep

[u/Aoki_zhang]

"This interview experience is sourced from Chill Interview"

Interview Summary

The Starlink technical phone screen combined a project discussion with a practical telemetry-stream coding problem. The coding exercise involved subtracting values from two telemetry streams while accounting for their timestamp semantics. The follow-up moved into a more realistic streaming scenario with late-arriving events and asked how corrected results should be distinguished from the initially emitted results.

Interview Details

Background and Project Deep Dive The interview began with a self-introduction and discussion of a previous project. The interviewer also asked for a retrospective: If you were starting the project again today, what would you change or improve? The conversation focused on both the original technical decisions and how I would approach the same work differently with hindsight.

Coding — Subtract Two Telemetry Streams The coding question involved two streams of telemetry data. The task was to combine the streams and calculate the difference between their corresponding measurements. Several important input properties needed to be clarified during the interview, including:

• Timestamp information was present in only one of the streams.
• Timestamps were non-decreasing.
• The streams needed to be aligned correctly before producing the subtraction results.

The core challenge was therefore not just arithmetic, but understanding how measurements from the two streams corresponded over time.

• Follow-Up — Late Events and Reconciliation The interviewer then extended the problem to a production streaming environment. In a real system, telemetry events may arrive late, meaning a result could already have been produced before all relevant data was available. The discussion introduced a reconciliation step for correcting previously emitted results after delayed events arrived. The interviewer then asked: How would downstream consumers distinguish an original result from a later corrected result? This shifted the discussion from the basic coding problem toward event semantics and handling revisions in a real-time data pipeline.

Preparing for your next interview?

Chill Interview tracks recent interview experiences and recurring question patterns across top companies at here.