Software Engineer - SDK

We built Moss because Voice AI breaks when retrieval is slow. Most retrieval infrastructure was not built for real-time reasoning. It adds latency, breaks context mid-conversation, and becomes the bottleneck just as an AI product needs to feel instant.

Moss is the real-time semantic search layer for conversational AI. We deliver sub-10ms retrieval directly in the browser, at the edge, on-device, or in the cloud, without making teams stitch together a slow retrieval stack.

We are backed by YC and run in production for teams building serious AI products. Moss is deployed across 100+ countries, serves 5M+ of real-time voice minutes, supports enterprises serving 3000+ of their own end customers, and has 380K+ package installs.

The SDKs are how every one of those developers meets Moss. They are the first thing a team touches, the surface that has to feel instant on every platform, and the layer where our Rust engine becomes real code running inside someone else's product.

We are looking for a Senior or Staff SDK Engineer to own how Moss ships across every developer surface: JavaScript/TypeScript, Python, Swift, Android, Elixir, C, and the Rust core they all bind to.

This is not a greenfield role. You will work on live SDKs that customers depend on in production from day one: shrinking bundle size, lowering cold-start and query latency, tightening cross-platform parity, improving developer ergonomics, and making integration effortless across browsers, servers, mobile devices, edge runtimes, and embedded environments.

When milliseconds and correctness are both part of the product, and your code runs inside someone else's application, your work defines whether teams trust Moss.

What you'll do

• Own the architecture and evolution of Moss SDKs across multiple programming languages and platforms.
• Design and maintain safe, ergonomic bindings around our Rust core.
• Build and improve FFI layers, packaging systems, release pipelines, versioning strategies, and developer tooling.
• Ensure consistent APIs and behavior across all supported SDKs while respecting platform-specific constraints.
• Push performance boundaries across memory usage, startup latency, binary size, and runtime efficiency.
• Work directly with customers to debug production issues across diverse environments and operating systems.
• Establish engineering standards for testing, compatibility, benchmarking, observability, and long-term maintainability.
• Help shape how developers experience Moss from the first npm install to production deployment.

What we're looking for

• Deep systems engineering experience with strong fundamentals in performance, memory management, concurrency, and low-level debugging.
• Significant experience in Rust and building production systems that interface with multiple programming languages.
• Proven track record shipping SDKs, libraries, runtimes, databases, or developer infrastructure at massive scale.
• Experience building products that have run on hundreds of millions to billions of devices, users, or installations.
• Comfortable moving across language ecosystems and technology stacks without being constrained to a single environment.
• Strong understanding of FFI, language bindings, package distribution, build systems, and cross-platform development.
• Experience with one or more of: JavaScript/TypeScript, Python, Swift, Kotlin/Android, C/C++, Elixir, or other systems languages.
• Ability to operate with high ownership in ambiguous environments and make pragmatic engineering tradeoffs.

Bonus points

• Experience building mobile SDKs or embedded/on-device AI infrastructure.
• Experience with WebAssembly, native mobile runtimes, edge environments, or browser internals.
• Background in search, databases, AI infrastructure, compilers, or developer tooling.
• Experience maintaining highly adopted open-source libraries or SDKs.
• Prior experience as a Staff+ engineer responsible for platform or SDK strategy across an organization.

What success looks like

In your first 30 days

• Develop a deep understanding of Moss's architecture, retrieval engine, and SDK ecosystem.
• Become familiar with our Rust core, FFI boundaries, release pipelines, and supported platforms.
• Ship your first production improvements to one or more SDKs.
• Work directly with customers and internal teams to understand integration pain points and performance bottlenecks.

In your first 60 days

• Own one or more SDK surfaces end-to-end.
• Improve developer experience, reliability, or performance in meaningful ways, such as reducing startup latency, binary size, or integration complexity.
• Propose and begin executing on a roadmap for cross-platform consistency and SDK architecture improvements.
• Establish stronger standards around testing, compatibility, benchmarking, and release engineering.

In your first 90 days

• Become a technical owner for major portions of Moss's developer platform.
• Drive strategic initiatives around SDK architecture, cross-language bindings, packaging, and developer tooling.
• Deliver improvements that materially impact adoption, reliability, and production performance.
• Help define how Moss reaches browsers, servers, mobile devices, edge environments, and eventually billions of devices.
• Raise the engineering bar across systems design, developer experience, and operational excellence.

Why this role matters

Moss is becoming infrastructure that sits directly in the critical path of real-time AI systems. Every millisecond matters. Every platform matters.

The SDK layer is what turns our retrieval engine into something developers can trust and deploy everywhere.

You will not be maintaining wrappers around APIs.

You will be defining how real-time retrieval infrastructure reaches millions of applications and, eventually, billions of devices.