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Amazon·Software Engineer·Technical Phone Screen·Senior

Senior
Apr 2026

Summary

Amazon embedded software interview with a pretty gnarly system design question about heterogeneous multicore scheduling. Not the typical LeetCode grind, more of an open-ended architecture discussion that left me second-guessing myself for a while after.

Questions Asked (1)

Q1

You have a non-symmetric multiprocessor system where some cores only handle division and others have hardware acceleration for both multiplication and division. Given a batch of vectorized arithmetic operations, how would you design an algorithm to assign operations to cores for near-optimal total execution time? Walk through your cost model, heuristic choices, and the trade-offs involved.

System DesignAlgorithms & Data StructuresTechnical Trade-offs
Author's notes

This one took me a second to even parse.

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AI HintsAI Generated

Suggested Approach

Start by defining a clear cost model that captures core capabilities and operation types, then formulate the assignment as an optimization problem. Propose a practical heuristic like list scheduling or greedy assignment, and discuss trade-offs between optimality and complexity, including load balancing and communication overhead.

Pro tip: Emphasize that in real systems, the cost model must be calibrated with benchmarks, and that a simple heuristic with good constants often beats a complex optimal algorithm due to overhead and unpredictability.

1. Define the cost model

Characterize each core's capabilities (division-only vs. multiplication+division acceleration) and assign execution costs per operation type. Include factors like throughput, latency, and any data transfer costs.

2. Formulate the assignment problem

Model the problem as minimizing total execution time (makespan) by assigning each operation to a core, considering dependencies and core constraints. This is a variant of scheduling on unrelated machines.

3. Choose a heuristic

Select a practical algorithm such as list scheduling, greedy assignment based on cost ratios, or linear programming relaxation. Justify why it balances near-optimality with computational feasibility.

4. Analyze trade-offs

Discuss trade-offs: optimality vs. runtime of the algorithm, static vs. dynamic assignment, load balancing vs. specialization, and handling of communication or synchronization overhead.

5. Validate and iterate

Propose benchmarking and simulation to validate the cost model and heuristic, and describe how to adapt the algorithm if performance deviates from expectations.

Key Points to Mention

  • Cost model calibration with microbenchmarks
  • NP-hardness of unrelated machine scheduling
  • Heuristics: list scheduling, greedy, LP relaxation
  • Load balancing and makespan minimization
  • Communication and synchronization overhead
  • Dynamic vs. static assignment and adaptability

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.