SpaceX Software Engineer Full-Time C++ Pressure-Chamber Technical Screen

Role: Software Engineer
Result: Not disclosed
Report time: June 2025
Education disclosed: Computer science undergraduate degree and a master's degree in embedded systems

Before the interview

A recruiter called the candidate every day for about a week and repeatedly emphasized the software team's interest. The interview was introduced as a technical screen in C++, which led the candidate to expect a more conventional C++ discussion.

The question as presented

The interview instead opened with a short and ambiguous request to write an algorithm for a pressure-chamber system using velocity data from mission control during liftoff.

The prompt did not specify parameters, data types, expected results, or enough physical context to define the function. The candidate asked for clarification and additional context but reported receiving none.

Candidate approach and interviewer interaction

1. The candidate immediately outlined an approach and explained each step of the reasoning.
2. Linear interpolation was proposed to map velocity values to target pressure values.
3. The interviewer appeared dissatisfied and repeatedly interrupted with changes that the candidate viewed as unnecessarily complex and unrelated to the core calculation.
4. As the implementation approached completion, the candidate had a working main algorithm and created a table of test cases because none had been supplied.
5. The interviewer then asked for a different approach that changed variables directly instead of continuing with the nearly completed function.
6. The candidate asked for the intended meaning of that request. The interviewer became impatient, even though the main algorithm had already been acknowledged as correct.
7. The candidate continued adding the final code while explaining the remaining steps.
8. The interviewer abruptly ended the call with about 20 minutes still left in the scheduled meeting.

The call ended without a further discussion of the candidate's résumé, relevant experience, or the accuracy of the completed solution. The candidate viewed the question as poorly specified and the interaction as unprofessional and adversarial.

Clarification shared after the interview

The candidate later supplied the missing task shape:

• Changes in velocity map to a target pressure-chamber value.
• One disclosed point was 0.0 m/s → 120.0 bar.
• Another disclosed point was 100 m/s → 300.0 bar.
• The known minimum and maximum values were intended to anchor a lookup table.
• Sudden pressure fluctuations had to be avoided because they could cause an explosion.
• Pressure between known velocity points was to be estimated with linear interpolation.

For known points (x0, y0) and (x1, y1), the reported calculation was:

y = y0 + ((x - x0) * (y1 - y0) / (x1 - x0))

Here, x represents velocity and y represents pressure.

The report does not provide the complete table, the exact callable interface, the number of query velocities, behavior outside the known range, input-size limits, or a floating-point tolerance.

The corresponding FastPrep exercise is Pressure Chamber Linear Interpolation.