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Zipline·Software Engineer·Take-home Assignment·Senior

Senior
May 2026

Summary

Take-home assignment for a software engineering role at Zipline. The task was to implement a Kalman filter in Rust, specifically targeting embedded systems constraints, with a heavy emphasis on code quality and data-oriented design.

Questions Asked (1)

Q1

Implement a Kalman filter in Rust optimized for embedded systems, with a focus on code quality, engineering rigor, and a data-oriented design approach.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying the embedded constraints (MCU, memory, real-time deadlines) and the filter's state dimension, then propose a data-oriented design with fixed-size arrays and no dynamic allocation. Walk through the implementation in Rust, emphasizing zero-cost abstractions, predictable memory layout, and rigorous testing. Conclude by discussing trade-offs between numerical stability, performance, and code maintainability.

Pro tip: Mention that you would use const generics to parameterize the state dimension at compile time, enabling stack-allocated arrays and eliminating runtime bounds checks—a detail that shows deep Rust and embedded expertise.

1. Clarify Requirements and Constraints

Ask about the target MCU (e.g., Cortex-M), available memory, real-time deadlines, and the state vector dimension. Confirm whether floating-point hardware is available or if fixed-point arithmetic is needed.

2. Design Data-Oriented Structures

Propose using fixed-size arrays (e.g., [f32; N]) and const generics to represent matrices and vectors, ensuring all data is stack-allocated and cache-friendly. Avoid heap allocation and dynamic dispatch.

3. Implement the Kalman Filter Algorithm

Outline the predict and update steps using in-place operations and iterators to minimize allocations. Use Rust's ownership and borrowing to enforce safety without runtime overhead.

4. Optimize for Embedded Performance

Discuss loop unrolling, SIMD (if available), and avoiding floating-point operations where possible. Consider using nalgebra or a custom linear algebra module tailored to the state size.

5. Ensure Code Quality and Testing

Describe unit tests with known inputs, property-based testing for numerical stability, and static analysis (clippy, miri). Mention documentation and modular design for maintainability.

Key Points to Mention

  • Use of const generics for compile-time state dimension and stack allocation
  • Zero-cost abstractions and no dynamic memory allocation (no_std compatible)
  • Data-oriented design: struct-of-arrays vs array-of-structs, cache efficiency
  • Numerical stability techniques (e.g., Joseph form, square-root filtering)
  • Trade-offs between fixed-point and floating-point arithmetic on embedded targets
  • Testing strategies: unit tests, property-based tests, and hardware-in-the-loop validation

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