Principal Systems Engineer, Core Services (C#/Rust)

Showcify, Inc.

San Mateo (CA)

On-site

USD 345,000 - 399,000

Full time

4 days ago

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Job summary

Roblox is seeking a Principal Software Engineer for the Core Services team in San Mateo, CA. You will solve problems spanning distributed systems, concurrency, memory management, API design, and developer experience, with hands-on coding in C#/.NET and Rust.

You will build and evolve shared frameworks and libraries, investigate performance from application code through the runtime, design safe interop, create stable APIs, and lead cross-team initiatives from design through production adoption.

Qualifications

Deep production experience in C#/.NET or Rust, across both ecosystems.
Experience building reusable libraries, SDKs, frameworks, or runtime infrastructure adopted by multiple teams.
Strong fundamentals in concurrency, asynchronous programming, memory management, networking, and distributed systems.
A track record diagnosing complex production problems and delivering performance or reliability improvements.
Experience designing stable APIs and managing compatibility across dependent systems.
Demonstrated technical leadership: framing ambiguous problems, mentoring engineers, and driving cross-team execution.
Bachelor’s degree in CS or related field, or equivalent experience.

Responsibilities

Build and evolve shared C#/.NET and Rust frameworks, libraries, and SDKs.
Investigate performance from application code through the runtime: allocation pressure, garbage collection, lock contention, asynchronous execution, serialization, and network overhead.
Design safe, efficient managed/native interoperability with explicit ownership, error handling, cancellation, and compatibility contracts.
Create stable, usable APIs and lead their evolution across teams, balancing extensibility, performance, operational safety, and maintenance cost.
Build automation for framework upgrades and service migrations, including AI-assisted workflows supported by compatibility tests, benchmarks, traffic replay, and canary evidence.
Partner with deployment and service teams to make library changes easier to adopt, detect regressions early, and support safe rollout and rollback.
Lead ambiguous technical initiatives, mentor engineers, and measure outcomes in reliability, resource efficiency, adoption, and developer productivity.