Founding Full Stack Engineer Job at YC Work at a Startup (San Francisco)

Founding Full-Stack Software Engineer – AI for Biopharma

Founding Full-Stack Engineer role at Equator, an AI-native startup building next...

Location

Spain , Barcelona

Salary:

70000.00 EUR / Year

Blu Selection

Expiration Date

Until further notice

Requirements

4–6 years of software engineering experience (mid to senior level)
Strong backend engineering skills with Python
Proficiency in React, Next.js, TypeScript, Node.js
Experience building data-heavy or versioned backend systems
Strong clean-code discipline and architectural thinking
English (Advanced/C1+)
Valid Spain work permit (no sponsorship available)

Job Responsibility

Architect scalable, auditable backend systems (Python, PostgreSQL, modern frameworks)
Build APIs enabling seamless collaboration between humans and AI agents
Develop clean, modular frontend interfaces using React, Next.js, and TypeScript
Implement and maintain data-heavy systems and structured knowledge frameworks
Write clean, precise code and contribute to strong engineering standards
Collaborate closely with founders, designers, and early users to deliver impactful features
Influence product, technical direction, and architectural decisions as a founding engineer

What we offer

Gym membership

Fulltime

Senior Full Stack Software Engineer

Checkr Trust is seeking a Senior Full Stack Software Engineer to join their team...

Location

United States , San Francisco

Salary:

173000.00 - 215000.00 USD / Year

Checkr

Expiration Date

Until further notice

Requirements

BS/MS degree in either computer science or electrical engineering
have founded or held early roles at successful fast-paced startups
6+ years of full stack software development experience
advanced knowledge in Ruby (Ruby on Rails)/ Javascript (React), or similar languages/frameworks
amazing product sense
experimentation mindset
experience building scalable technical architecture that can scale to 10mm+ users

Job Responsibility

work closely with customers, engineers, and leaders to design, build, and launch new products
take full ownership of the entire process of developing end-to-end applications – from shaping the idea to delivering the finished application
build and improve APIs, including integrating with third-party services to expand what our products can do
embrace a customer-centric, product-first approach – partner directly with customer success, customers and stakeholders to better understand their needs and turn those into useful features
keep code reliable and easy to maintain with solid testing, thoughtful reviews, and good practices
run and measure product experiments, using what you learn to guide future development
building scalable APIs and asynchronous event-based architecture that can reliably handle very high traffic

What we offer

a fast-paced and collaborative environment
learning and development allowance
competitive compensation and opportunity for advancement
100% medical, dental, and vision coverage
up to 25K reimbursement for fertility, adoption, and parental planning services
flexible PTO policy
monthly wellness stipend, home office stipend
working at a startup within a startup
lunch four times a week
a commuter stipend

Fulltime

Founding DevOps Engineer

As a Founding Engineer with a DevOps focus, you will play a central role in buil...

Location

France , Paris

Salary:

60000.00 - 80000.00 EUR / Year

Blu Selection

Expiration Date

Until further notice

Requirements

Strong full-stack engineering background with a DevOps mindset
Hands-on expertise in cloud platforms (GCP ideal): deployments, infra, CI/CD
Proficient in TypeScript and Python
Experienced with React, Next.js, and FastAPI
Solid knowledge of PostgreSQL and Redis
Ability to design scalable systems and deliver production-grade code quickly
Comfortable using AI-assisted coding tools (Cursor, Claude Code, Copilot)
Thrives in fast-moving, ambiguous, 0→1 environments
Fluent in English (French is a plus)

Job Responsibility

Build fast, lightweight, and reliable front-end applications (React)
Develop backend services powering conversational and AI-driven experiences
Design and maintain scalable cloud infrastructure (preferably GCP)
Set up CI/CD pipelines, observability, monitoring, and infra-as-code
Optimize performance, reliability, and security across systems
Own core architectural decisions and enforce best engineering practices
Ensure code quality, stability, and scalability from the ground up
Collaborate closely with early users and customers to iterate quickly

Fulltime

Founding iOS Engineer

Babylist is looking for a Senior iOS Engineer to join our newest venture—a stand...

Location

United States , Needham

Salary:

180100.00 - 225082.00 USD / Year

Babylist

Expiration Date

Until further notice

Requirements

Strong understanding of software development principles, capabilities, and limitations of the iOS platform
Well-versed in the intricacies of iOS development and can navigate its unique features and constraints
8+ years of proven experience in iOS app development using Swift
Comfortable working with Swift and SwiftUI and have a deep understanding of syntax, features, and best practices
Familiar with Foundation, SwiftUI, CoreAnimation and other foundational Apple frameworks and patterns
Hands-on experience with SwiftUI, Previews, and rapid prototyping
Passion for building consumer-facing products and moving quickly in the zero-to-one of a new product
Experience with AI-driven software development practices and tools
Solid understanding of the Android ecosystem, with direct Android development experience being a plus
Comfortable and enthusiastic about working in an AI-forward environment where AI tools are part of daily operations

Job Responsibility

Conceptualize, design and develop our new standalone iOS app, taking ownership of the entire development lifecycle
Develop features and functionality, ensuring a seamless and delightful user experience
Collaborate closely with your designer and product manager to translate requirements into technical specifications and user-friendly interfaces
Transform concepts and designs into intuitive and visually appealing iOS app interfaces
Collaborate closely with a full-stack web engineer to align on architecture, API design, and more
Write clean, efficient, and maintainable code following industry best practices and coding standards
Employ various testing techniques, write unit tests, and leverage debugging tools to identify and address any issues or bugs
Collaborate effectively with team members, actively participating in discussions and brainstorming sessions
Contribute to feature ideation, and providing insights to the team

What we offer

Competitive salary with equity and bonus opportunities
Company-paid medical, dental, and vision insurance
Retirement savings plan with company matching and flexible spending accounts
Generous paid parental leave and PTO
Remote work stipend to set up your office
Perks for physical, mental, and emotional health, parenting, childcare, and financial planning

Fulltime

Senior Software Engineer, Checkr Trust

Checkr Trust is building safer communities by providing our customers with risk ...

Location

United States , San Francisco

Salary:

173000.00 - 215000.00 USD / Year

Checkr

Expiration Date

Until further notice

Requirements

BS/MS degree in either computer science or electrical engineering
Have founded or held early roles at successful fast-paced startups
6+ years of full stack software development experience
Advanced knowledge in Ruby (Ruby on Rails)/ Javascript (React), or similar languages/frameworks
Amazing product sense
Experimentation mindset
Experience building scalable technical architecture that can scale to 10mm+ users (including observability tooling, container orchestration, etc)

Job Responsibility

Work closely with customers, engineers, and leaders to design, build, and launch new products
Take full ownership of the entire process of developing end-to-end applications – from shaping the idea to delivering the finished application
Build and improve APIs, including integrating with third-party services to expand what our products can do
Embrace a customer-centric, product-first approach – partner directly with customer success, customers and stakeholders to better understand their needs and turn those into useful features
Keep code reliable and easy to maintain with solid testing, thoughtful reviews, and good practices
Run and measure product experiments, using what you learn to guide future development
Building scalable APIs and asynchronous event-based architecture that can reliably handle very high traffic

What we offer

A fast-paced and collaborative environment
Learning and development allowance
Competitive compensation and opportunity for advancement
100% medical, dental, and vision coverage
Up to 25K reimbursement for fertility, adoption, and parental planning services
Flexible PTO policy
Monthly wellness stipend
Working at a startup within a startup
In-office perks (lunch four times a week, a commuter stipend, snacks and beverages)
A relocation stipend may be available

Fulltime

Founding AI Engineer

Flint is defining the next generation of websites: ones that can constantly buil...

Location

United States , San Francisco

Salary:

150000.00 - 250000.00 USD / Year

Flint

Expiration Date

Until further notice

Requirements

You are a product-first engineer
You have built and deployed AI products that real users depend on
You have extensive hands-on experience with prompt engineering, context optimization, and model fine-tuning
You have strong full-stack engineering skills with experience integrating AI into web applications
You regularly use AI IDEs like Cursor or Windsurf to code
You take ownership of problems from start to finish and are eager to learn whatever you need to succeed
You’re comfortable in a fast-paced environment with evolving requirements
You have enthusiasm for building MVPs and iterating based on user feedback

Job Responsibility

Designing and implementing production-grade agentic systems that power web experiences and marketing workflows, leveraging advanced prompt engineering and multi-agent architectures to do so
Architecting and optimizing RAG (Retrieval-Augmented Generation) systems with context engineering
Strengthening our engineering processes through robust evals, observability, and testing
Developing and maintaining the core application across frontend, backend, and infrastructure
Shaping our technical vision and leading architectural discussions. You'll make foundational decisions that influence both Flint's technical architecture and engineering culture.
Creating and testing prototypes to gather rapid feedback from users

What we offer

Historic office in Jackson Square (with 2 rooftops and a shower)
A crazy upside-down battlestation
20 PTO days a year and full health benefits
Lunch and a fully stocked snack bar at the office, incl. Cometeer coffee pods
Dog friendly
Competitive salary + equity

Fulltime

Founding Engineer (Full Stack Web)

Pax Historia is an alternate-history sandbox game where players choose a country...

Location

United States , San Francisco

Salary:

150000.00 - 215000.00 USD / Year

YC Work at a Startup

Expiration Date

Until further notice

Requirements

Extremely comfortable with cross-functional full-stack development
Able to think through problems, create workable solutions, and debug complex code on your own
Experience using NextJS
Experience using Typescript
Experience using Firestore
Experience using Supabase
Experience using R2
US citizen/visa only
1+ years experience

Job Responsibility

Help build and improve the customer experience of paxhistoria.co
Frequently help with other ad-hoc projects as needed

What we offer

0.25% - 1% equity
12 month cliff and 4 year monthly vesting
Non-matching 401k plan

Fulltime

New

Founding Engineer

As a founding engineer and first full-time hire, you’ll be a cornerstone in buil...

Location

United States , San Francisco

Salary:

120000.00 - 180000.00 USD / Year

YC Work at a Startup

Expiration Date

Until further notice

Requirements

3-5 years of experience as an engineer shipping full stack solutions in an elite, high velocity team
1+ years of experience deploying LLMs (ideally voice AI) to production for thousands of users
Experience with some of our tech stack: Python, FastAPI, Typescript, Next JS, Docker, MongoDB, AWS (ECS Fargate), OpenAI embeddings, LiveKit, Twilio
A degree or significant coursework in a quantitative subject (CS, math, statistics, physics, engineering)
Demonstrated exceptional intellect: Examples could be a 4.0 GPA from top institution, placing in Putnam Top 500, competitions like USAMO, USACO Platinum, or programs like RSI, ISEF, Regeneron STS

Job Responsibility

Ship full-stack and AI features at a blistering pace (we use Python FastAPI and Typescript Next.js)
Navigate extreme ambiguity and coordinate with founders, other platform engineers, and FDEs to build a cohesive roadmap
Lead the development of new product verticals as we expand our footprint and build towards our vision of creating the AI operating system for cities
Design scalable and reliable system architectures for core platform capabilities
Respond to system issues promptly, identify root causes, and turn lessons into a more resilient system
Manage and streamline cloud deployments through the refinement of our CI/CD pipeline and cloud infra
Talk directly to customers and unearth immediate pain points, core problems, and future opportunities, reading between the lines when necessary
Be receptive to brutal feedback and changes in course (even if it invalidates previous work)
Add polish and delight when you sense a high-leverage opportunity, or just want to have fun (don’t 80/20 everything)
Get excited about people problems - interviewing, evaluating, and mentoring new engineering hires

Fulltime

Founding Full Stack Engineer

YC Work at a Startup

Location:
United States , San Francisco

Category:
IT - Software Development

Contract Type:
Not provided

Salary:

Job Description:

Job Responsibility:

Requirements:

Nice to have:

Additional Information:

Job Posted:
February 14, 2026

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