Spacex Software Engineer
Interview Guide

What is the difference between a stack and a queue, and what is the Big O time complexity for inserting an element into a queue?

Explain how an asynchronous FIFO works, and detail how Gray code conversion is used to handle pointers across clock domains.

Describe the difference between a Hardware Description Language (HDL) like Verilog and a high-level software language like C++ or Python.

How does a clock cell differ from a standard cell in ASIC design, and what is clock latency?

Explain the concepts of Static Timing Analysis (STA) and how you would go about speeding up a critical timing path.

How does a voltage regulator work, and how would you draw the block diagram for an Electronic Control Unit (ECU) you have previously worked on?

Write an algorithm to handle a pressure chamber system using velocity data received from mission control during liftoff.

Given an array representing stock prices over time, write a function to find the maximum profit you can achieve from a single buy and sell transaction.

resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.

outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.

A flat steel plate is suspended by four hockey pucks in the corners. Describe the stresses that develop in the plate. Where are they at a maximum, and where are they at a minimum? What happens if the hockey pucks are replaced with steel blocks?

Explain the relationship between stress and strain. What are the primary failure modes of a cantilever beam under a point load?

What physical changes in pressure are required to double the mass flow rate of an incompressible fluid through a pipe?

Explain the difference between compressible and incompressible flow, and how the ideal gas law applies to transient combustion.

Design an optimization algorithm for satellite configuration based on specific signal beam constraints and pointing angles.

How would you adapt a testbench to handle protocol changes, such as migrating from an AXI to an AHB bus interface?

Describe how you would design a software system to dry clothes using first principles, assuming you cannot use standard commercial dryer architectures.

During a release on PostgreSQL, every query touching resource times out for about 40 seconds and then recovers with no intervention. The release ran one migration, ALTER TABLE resource ADD COLUMN archived_reason TEXT, and the migration log shows it completing in 6 ms. Unrelated tables showed no change in error rate. Explain how a 6 ms statement caused a 40-second stall, give the ordered checks you would run on a live system to confirm it, and give the migration procedure that prevents a repeat.