Principal Software Engineer

Realtime TTS-2 is the #1 model on Artificial Analysis and the fastest TTS in the world of its class. Watch the launch video Staff / Principal Software Engineer - USA Mountain View, California, USA

About Inworld

Inworld is a research lab of top researchers and engineers, building the world’s top-ranked realtime voice models.

Today our models are the #1 ranked realtime voice models in the world. They are used to power the largest consumer-facing AI applications available, across categories like health, fitness, learning, therapy, companions, customer experience and media; representing 100s of millions of end users. Our work spans areas like research and development of state-of-the-art models, optimizing realtime inference, and creating best-in-class APIs and products that allow developers to engage their users.

We’ve raised more than $125M from Lightspeed, Section 32, Kleiner Perkins, Microsoft’s M12 venture fund, Founders Fund, Meta and Stanford, among others. Our technology has powered experiences from companies such as NVIDIA, Microsoft Xbox, Niantic, Logitech Streamlabs, Wishroll, Little Umbrella and Bible Chat. We’ve also been recognized by CB Insights as one of the 100 most promising AI companies globally and have been named one of LinkedIn’s Top 10 Startups in the USA.

About the role:

Inworld recently launched a few exciting new products (Inworld TTS , Inworld STT , Speech-to-Speech / Realtime API and Inworld Router ) for consumer AI applications, and we're looking for an ambitious and capable Staff/Principal Backend Engineer to join us and help take the Inworld AI platform even farther. Here is what you are going to work on:

• Inworld Router : an intelligent routing layer that gives developers a single API to access 200+ LLMs. You'll own core systems for multi-provider failover, cost/latency-based routing, live A/B experimentation, and real-time observability at massive scale.

• Realtime API

• API-based model services : Our custom TTS/STT models and API includes free instant voice cloning. Learn more and hear examples atinworld.ai/tts . Better yet, sign up yourself atplatform.inworld.ai , try out the premade voices, clone your own voice in just a few seconds, and let us know what you think! Beyond TTS, there is also LLM, Knowledge/RAG, STT, and more.

• New exciting products , ambitious and large-scale, in the lineup for the launch later this year.

• Services for control and optimization . We're just getting started on these deeper capabilities.

• Infrastructural projects : platformization of new product upcoming offering, development and integration of best development tools, projects like system-wide billing and so on.

As a Staff/Principal Software Engineer, you would be a significant part of one or more of these areas. The key challenges are:

• Shipping quickly . AI is evolving weekly, so there's a ton of opportunity to be had. We want to move fast to capture those opportunities while they are still fresh and full of potential.

• Zero to one . The platform is not a simple copycat. We have a vision for a deep platform/suite of capabilities that make it dramatically simpler for developers to scale and evolve their AI.

• Realtime, online . As consumer applications become more capable of listening and talking, performance will matter, and AI has to adapt in realtime as well. These are bold but exciting challenges.

• Multi-provider complexity at scale . Inworld Router must intelligently route across hundreds of models and providers while handling failover, sticky sessions, cost optimization, and conditional logic, all with minimal latency overhead. You'll design systems where every millisecond and every routing decision matters.

Finally, almost everything here is a collaboration with our sibling ML teams, since ML and AI are critical to providing the learning and adaptability central to this vision.

Please note: This is an IC-focused role. We are looking for someone who loves direct technical contribution alongside very capable peers.

What you’ll do:

• Establish significant scope : Collaborate with the PMs, engineers and leads to determine the biggest product needs to focus on now.

• Operate with technical autonomy : You have considerable leeway to suggest how to address a given focus area, including bringing in new technical dependencies or standards where it's the best choice.

• Collaborate, execute, deliver : This is the core of the building loop. We aim to optimize for both speed and quality, despite it being decidedly non-obvious how to manage that tradeoff exceptionally well.

• Reflect and drive improvements: Especially as a Staff Engineer, advocate for and realize system improvements, both related to and independent of key features.

Expected experience:

Must Haves

• Excellent programming skills and experience in a statically typed backend programming language, preferably Go, Python, C++ or Rust

• Experience developing and deploying cloud-based services to at least hundreds of qps (preferably more)

• Experience with relational databases (PostgreSQL or MySQL)

• Hands-on experience with caching (Redis or Memcached), pubsub/queues, data pipelines (Flink, Beam), and Cloud storage

• Excellent verbal and written communication skills, can collaborate and coordinate with other roles and engineer with ease, trusted and well-regarded teammate

Bonus Qualifications

• Experience building API gateways, routing/proxy layers, or multi-provider orchestration systems

• Experience with analytics or timeseries databases (ClickHouse, Timescale, InfluxDB)

• Experience with OpenTelemetry

• Experience with C++

Candidates must be based in the SF Bay Area or willing to relocate (you will be working on-site in our South Bay office a few days a week).

The US base salary range for this full-time position is $280,000 - $350,000. In addition to base pay, total compensation includes equity and benefits. Within the range, individual pay is determined by work location, level, and additional factors, including competencies, experience, and business needs. The base pay range is subject to change and may be modified in the future.