Senior Platform Engineer

TechTree; San Francisco (CA); On-site; USD 180,000 - 240,000; Full time

Benefits offered by this job

Health insurance

Dental

401(k) plan

Generous PTO

Gym budget

Lunch

Job summary

TechTree in San Francisco (Presidio) is seeking a senior backend engineer to build the agent runtime that coordinates tool calls, sessions, and long-running tasks. You will decide when work lives as an actor or a job, and shape how code changes resume in-flight processes.

This role emphasizes production-grade systems, concurrency, and robust tracing, with a focus on TypeScript, Cloudflare Workers, and a durable execution model. In-person, 5 days/week in the Bay Area.

Qualifications

• Experience building stateful backend systems in production.
• Ability to explain the tradeoffs between actors, background jobs, or simpler services.
• Experience debugging concurrency, retries, or recovery in code you own.
• Proficiency with TypeScript and backend-focused tooling.

Responsibilities

• Agent runtime: build and improve the runtime that starts agent work and carries session state across tool calls.
• Actors vs. jobs: choose between actors and jobs for different work and handle overlapping sessions.
• Deploys with work in flight: design long-running processes that drain or resume across releases.
• Retries and timeouts: handle failure around tool calls, including partial successes.
• Traceability: make runtime failures traceable and fix execution paths in production.

Skills

TypeScript

Backend systems

Concurrency handling

System design

Tools

Cloudflare Workers

Durable Objects

Postgres

Docker

Job description

Every tool you use was built as an island, so you became the glue between them: a name from Gmail into the CRM, a time from the CRM into Calendly, a note from Calendly into a doc. AI showed up and mostly became an eleventh window to paste into.

We're building a hybrid of AI and software standing on one shared brain. It holds your context and hands you real software built on top of it, so an ordinary scheduling tool becomes one that writes the invite itself and knows which of your busy hours bend, and for whom. Software for the path you repeat, AI for the edge that never repeats.

We're a team of about 15, backed by top-tier investors and Y Combinator, building from an office in the Presidio in San Francisco, a short walk from Crissy Field beach. We work absurdly hard because we can see and feel the outcome every day.

About the role

Our agent runtime has to keep track of work when a tool fails or new code ships mid-task. One session might start with a message, check Calendar, draft a Slack reply, and update Linear after the first response. A tool call can time out after the action succeeds; the runtime needs to know what happened before retrying.

You'll build the execution engine behind those sessions, choosing when work belongs in an actor and when a job is enough. You'll also design how long-running processes deploy while other tasks are in flight.

This is a senior, hands-on engineering role. You'll make those calls with the team, write the code, and own it in production. We'll teach you our agent harness.

What you'll do

Agent runtime - build and improve the runtime that starts agent work, carries session state through tool calls, and resumes interrupted runs.

Actors vs. jobs - choose between actors and jobs for different kinds of work, implement the choice, and check how it behaves when sessions overlap.

Deploys with work in flight - design how long-running processes drain or resume when code changes, keeping in-flight work accounted for across releases.

Retries and timeouts - handle failure around tool calls, including cases where an external action succeeded but the response never came back.

Traceability - make runtime failures traceable: find why a run stopped or stalled, fix the execution path, and see the change through to production.

Stack: TypeScript, Cloudflare Workers, Durable Objects, Postgres, Docker. Experience with comparable runtimes counts.

What we're looking for

You've built and operated stateful backend systems in production, including work that outlasts the request that started it.

You can explain a decision you made between an actor, a background job, or a simpler service, and show what you shipped.

You've debugged concurrency, retries, or recovery in code you've owned.

You're productive in TypeScript and want to keep writing code as your scope grows.

Bonus:

You've worked on an agent runtime or agent harness.

You've worked with Cloudflare Workers, Durable Objects, or another actor-based runtime.

You've deployed long-running processes that persist or resume work across a code release.

Logistics

Location: San Francisco (Presidio) - in-person, 5 days a week in the office.

You must be based in the Bay Area or willing to relocate before starting.

US work authorisation required; open to O-1 or J-1 visa sponsorship for exceptional candidates.

Compensation: $180K-$240K base + meaningful early-stage equity, plus health, dental, 401(k), considerable PTO, gym budget, and lunch.

Our process

Exceptional candidates go from first touch to offer within two weeks.

Application - resume and a few short questions.

45-minute technical interview - a real backend problem. We're looking for fluency, depth, and how you think about systems.

System design interview - we walk through a real architecture problem of ours together.

Final conversation - your questions, and we scope the work trial.

Paid work trial - in person, usually a few days to two weeks, on a real project. See how we work and whether it's the right fit on both sides.