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

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

New

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

New

Founding Engineer (Full-Stack)

Companies waste billions on bad ads, mismatched landing pages, and poor budget a...

Location

United States , San Francisco

Salary:

150000.00 - 200000.00 USD / Year

YC Work at a Startup

Expiration Date

Until further notice

Requirements

Bachelor’s or Master’s degree in Computer Science or a related field, or equivalent practical experience
Minimum of 2 years full-time experience in software engineering, preferably in early-stage startups
Frontend Expertise: Proficiency in building responsive frontends using React/Next or Vue.js and the Nuxt framework
Backend Expertise: Strong backend development skills in TypeScript/Node.js and experience with PostgreSQL or relational databases
Strong creative judgment with a sense for marketing
Demonstrated ability to work independently
Based in or willing to relocate to San Francisco
on-site presence required (Visa sponsorship will be provided if needed)

Job Responsibility

Full-Stack Development: Design, build, and maintain scalable applications using Node.js, TypeScript, and Nuxt (Vue)
System Architecture: Architect and manage robust database schemas with PostgreSQL and Supabase, ensuring data integrity and performance
Infrastructure & Operations: Manage deployments and background jobs using Render and Inngest, and assist in maintaining dedicated deployments on Microsoft Azure
Product Ownership: Own projects across the full lifecycle, including concept development, implementation, deployment, and ongoing maintenance
User-Centric Design: Apply sound product and design judgment to build user-centric software features aligned with current market and customer needs
Collaboration: Collaborate closely with the operations team and customers via Slack and Notion to ensure technical solutions are aligned with user requirements

What we offer

Be one of the first employees at a well-funded startup
Solve a massive problem in a massive market
Take ownership and grow quickly
Culture: fast-moving, ambitious, fun, humble

Fulltime

New

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: Product-Focused Full-Stack Developer

You lean toward product, UX, and the user experience. You’ll build the interface...

Location

Netherlands , Amsterdam

Salary:

75000.00 - 130000.00 EUR / Year

YC Work at a Startup

Expiration Date

Until further notice

Requirements

Can own features end-to-end and enjoy doing so
Ship fast and care about quality, clean architecture, solid tests, good UI
Resourceful and persistent, figure things out
Have built things you're proud of (products, open source, side projects)
Use AI tools daily and want to keep raising that bar
Think in systems and multipliers, not just tasks

Job Responsibility

Ship production features across the stack
Work in tight loops: build → test → measure → refine
Use AI tools daily (Cursor, Claude, etc.) and push them further
automate glue work, generate scaffolds, build evals, multiply your own output
Take ownership of outcomes, not tickets

Fulltime

New

Senior Software Engineer

Arqit is a global cybersecurity company delivering quantum-safe encryption to se...

Location

United Kingdom , Belfast

Salary:

Not provided

Arqit

Expiration Date

Until further notice

Requirements

Significant commercial experience of developing complex enterprise software and services
Demonstrable experience in building horizontally-scalable mission-critical enterprise software and services, preferably in a startup environment
Experience of cloud service development (public/hybrid/private cloud PaaS or SaaS)
Extensive experience of Python programming and best practice
Demonstrable passion for software development through self-learning, personal projects, competitions etc.
Experience of triage, RCA and fix for software issues within a distributed system
Competence in multiple programming languages
Experience of database development (SQL and NoSQL)
Experience with design patterns, refactoring, OO design and related areas
Strong analytical, problem-solving and organizational skills

Job Responsibility

Developing software for our Encryption Intelligence technology, working under the guidance of our software architects and other senior colleagues
Transforming architectural models into component designs ready to be incrementally developed, tested and deployed
Collaborating closely with our team of software, automation and DevOps engineers to implement, review, test and deploy full-stack software changes
Working extensively with Python, you will have the opportunity to train on Rust and AngularJS
Analysing the metrics of your deployment changes, ensuring high resiliency and performance is maintained, resolving issues if they arise
Fixing issues found internally and by our customers
Actively participating in Agile development activities and rituals, supporting the growth of the team and its members
Being open to receiving feedback and being willing to offer constructive feedback and support to others
Working closely with the Product Management team to help further refine requirements

What we offer

25 days paid holiday
8 bank holidays
Pension
Private Medical Insurance
Life Insurance
Income Protection
Employee Assistance Programme
Coaching
Parental Leave
Personal Travel Insurance

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:
January 07, 2026

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