Senior Fullstack Engineer

Meet Siena
Siena is the Agent of Record for CX, built for consumer brands like Spanx, FIGS, Brooklinen, and Grüns.
It runs as a connected multi-agent stack on top of a shared intelligence layer: agents that sell, support, listen, handle social and voice across the entire customer journey, turning every conversation into signal you can act on.
The team
We are a small, fully distributed, global team. We have built leverage into how we work, which is what lets a team this size move at the speed we do.
We hire athletes. Everyone here owns real outcomes, defaults to writing over meetings, communicates with directness, and acts the moment they see something worth acting on. Low ego, high standards, fast clock.
If you want to set the bar rather than follow one, keep reading.
The Role
You'll own meaningful parts of the platform end to end, taking ambiguous problems and shipping reliable, high-performance systems that real brands depend on daily. You'll work closely with product to shape scope, make real architectural calls in your area, and do your best work without being managed task by task. This is for engineers who want ownership and can carry it.
What You'll Do
Own features and systems across the full stack (frontend, backend, infrastructure) from problem definition through production.
Partner with product to break down ambiguous scope and ship in iterative, high-impact releases.
Make real architectural and design decisions in your area, and explain the reasoning so the team can build on it.
Take cutting-edge language models into enterprise customer workflows, where reliability and safety actually matter.
Solve hard engineering problems: API performance, microservices, scaling across channels and brands.
Maintain and improve our AWS infrastructure with a DevOps mindset.
Raise the bar around you. Share what you know, review thoughtfully, help teammates level up.
Who You Are
The Bar
: if you're missing any of these, this isn't the role for you
5+ years shipping and owning systems that are live in production, not personal projects.
Strong in our core stack: Node.js, React, TypeScript, Express.
You've shipped LLM-powered features to real users. This is a must, not a bonus. You know what breaks when models meet production traffic.
Strong Signal
: not dealbreakers, but what separates a good hire from a great one
Solid with AWS (Fargate, Lambda, EC2, SQS), PostgreSQL, and Redis.
Comfortable with CI/CD pipelines (CodePipeline, GitHub Actions, or similar).
Experienced with microservices and scalable systems.
Product-focused. You think past the code to customer outcomes and business impact.
High-ownership and direct. You fix problems without waiting to be told.
Nice to Have
: bonus, not required
Next.js.
Infrastructure as Code (CDK, Terraform).
Python.
Event-driven architecture.
Background in customer support or CX software.
Not a Fit If
You want tickets assigned to you and a clear spec before you start.
You've only worked on internal tools, never shipped something real users depend on every day.
You need a manager checking in regularly to stay motivated.
Why Siena?
Real ownership. You will own problems, not tasks, with the autonomy to solve them your way and the trust to do it without a manager in your inbox.
Work that ships and matters. What you build reaches real consumer brands fast.
A category we are creating. The Agent of Record is new ground, with unsolved problems and cutting-edge models, not a crowded field to compete in.
A team that respects your judgment. Globally distributed, async-first, low bureaucracy. We hire adults and treat you like one.
Great salary plus equity or stock grants. Own a piece of what you build.
Learning budget. If you are growing, so are we.
AI-fluency by default. Few places will push your work with production AI further or faster.
Our values
The people who thrive here are curious, customer-obsessed, and take ownership without being asked. They fix problems first and explain later. They're direct about feedback - both giving and receiving it - because they care more about getting things right than being polite.
They maintain high standards while moving at startup speed, and they build real relationships with teammates because they know that's how great work gets done. When things get tough, they adapt and keep pushing forward.
Our approach to AI
The people who thrive here treat AI like a natural extension of themselves. They've built their own ecosystem of agents - some for research, others for debugging, writing, analysis, or writing code. They know which AI works best for what problem.
Everyone gets premium accounts (ChatGPT, Claude, Perplexity Pro, Cursor, Lovable) plus a quarterly budget for new tools. But the magic happens in how we share knowledge. Demo days where someone shows off a clever workflows. Slack threads about which model handles a specific use case better. Learning from each other's AI workflows.
At Siena, we're not just looking for people who can do a job. We're looking for people who want to break boundaries, create the future, and reshape industries. If that's you, we look forward to your application.
How we hire
We use AI-assisted screening tools as part of our hiring process. All decisions are made by humans.
Siena provides equal employment opportunities to all employees and applicants for employment without regard to race, color, religion, sex, national origin, age, disability, genetics, sexual orientation, gender identity, or gender expression. We are committed to a diverse and inclusive workforce and welcome people from all backgrounds, experiences, perspectives, and abilities.
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