Python Flask React Jobs in California (NOW HIRING)

Job Summary:
Haus is the incrementality platform leading brands trust to optimize billions in ad spend worldwide. The Senior Full Stack Engineer will build and evolve systems that help brands understand the true impact of their marketing spend, working across a Python/Flask API and a React frontend.
Responsibilities:
• Own features end-to-end: from API design and database migrations through React UI and data visualization, all the way to monitoring and on-call support
• Build and harden integrations with third-party ad platforms (Meta, Google, TikTok) — design for reliability across APIs you don’t control
• Evolve and modernize a production Flask + React application that serves hundreds of customers — improve architecture incrementally while shipping continuously
• Design and build data-rich UIs: charts, dashboards, and interactive tools that help marketers understand complex experimental results
• Collaborate closely with scientists and data engineers to translate statistical outputs into product experiences customers can act on
• Use AI development tools as part of your daily workflow to accelerate delivery, explore solutions, and raise the ceiling on what you can ship
• Participate in on-call rotation and own the operational health of the systems you build
• Review code across the team and help set the bar for quality, clarity, and maintainability
Qualifications:
Required:
• 5–10+ years of experience building and shipping production web applications and APIs
• Strong across the full stack: you can build a well-structured API endpoint, write a database migration, and implement the frontend that consumes it
• Proficiency in Python and React (or strong equivalents with willingness to ramp); experience with Flask, SQLAlchemy, or similar frameworks is a plus
• Experience working in and improving large, established codebases — you’ve navigated legacy systems, made pragmatic tradeoffs between refactoring and shipping, and left things better than you found them
• Comfort with cloud-native environments (GCP preferred): you understand how to deploy, monitor, and operate services in production
• Experience with relational databases (MySQL/PostgreSQL) and data-heavy applications
• Track record of working effectively with AI development tools (Claude, Cursor, Copilot, or similar) — you’ve integrated them into your workflow and can articulate how they change the way you build software
• Strong product sense: you think about what customers need, not just what the ticket says
• Excellent communication skills — you can explain technical tradeoffs clearly and work effectively with scientists, product managers, and other engineers
• Demonstrated ability to lead technical direction for a system or product area, making architectural decisions that hold up as the team and product scale
• Experience driving cross-team or cross-system initiatives — you’ve coordinated changes across multiple services or repositories and managed the sequencing
• A track record of mentoring other engineers and raising the technical bar of the team through code review, design guidance, and leading by example
• Comfort operating with ambiguity: you can take a loosely defined problem, break it down, build the plan, and drive it to completion without heavy oversight
Preferred:
• Earlier stage startup experience
• Experience with ad platform APIs (Meta Marketing API, Google Ads API)
• Experience with data visualization or experimentation platforms — if you’ve built charts that help people understand data or worked on systems that run experiments, you’ll ramp faster here
• Experience with third-party data integrations and ETL workflows
Company:
Haus is a marketing science platform that helps brands understand the true business impact of their marketing spend. Founded in 2021, the company is headquartered in Mountain View, USA, with a team of 51-200 employees. The company is currently Growth Stage.