Principal Software Engineer, Core Services

Core Services builds the foundational services and software infrastructure behind Roblox’s global platform. Our work includes the C#/.NET and Rust frameworks, shared libraries, and runtime integrations that engineers use to build and operate production services.

As a Principal Software Engineer on the Core Services team you will solve problems spanning distributed systems, concurrency, memory management, API design, and developer experience. You will improve the performance and reliability of our C# ecosystem, expand our Rust infrastructure, and develop shared components and interoperability patterns across both languages. Your work will help teams adopt better foundations safely, with improvements that compound across Roblox’s service fleet.

This role combines hands-on systems engineering with technical leadership. You will work with service owners and infrastructure partners to turn complex platform capabilities into reliable, usable building blocks, and own their evolution from design through production adoption.

You Will

• Build and evolve shared C#/.NET and Rust frameworks, libraries, and SDKs, including HTTP/gRPC infrastructure, caching, configuration, and observability.
• 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.

You have

• Deep production experience in C#/.NET or Rust, with the ability and interest to work effectively across both ecosystems.
• Experience building and evolving 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 of diagnosing complex production problems and delivering measurable performance or reliability improvements.
• Experience designing stable APIs and managing compatibility, versioning, dependencies, and adoption across dependent systems.
• Demonstrated technical leadership: framing ambiguous problems, explaining tradeoffs, aligning stakeholders, mentoring engineers, and driving cross-team execution.
• A bachelor’s degree in Computer Science or a related field, or equivalent experience.

Particularly valuable experience

• .NET runtime internals, GC and allocation optimization, thread-pool behavior, or production profiling.
• Rust ownership and lifetimes, async runtimes, concurrent data structures, or performance-sensitive library design.
• Managed/native interoperability, FFI, native memory diagnostics, or cross-platform packaging.
• Contract-driven code generation, serialization, compatibility testing, or large-scale framework migrations.
• Automated validation and rollout of shared dependencies across a service fleet.