Just four years in, 25% of young women in the US (18-25) have downloaded Co–Star. Our growth has been entirely through word of mouth—we’ve never spent money on ads. We have millions of active users, raised $21,000,000 from the people behind companies like Twitter, Discord, and Snap, and launched our second paid feature. 

For thousands of years, astrology has given people the tools to reflect and connect in real, meaningful ways. Co–Star brings astrology into the 21st century with an app users call their “best friend” and therapists recommend to their clients. Astrology is a deterministic system based on the time it takes a planet to orbit the sun. It's more like folk developmental psychology than it is like fortune cookies. Using NASA data interpreted by humans, Co–Star delivers personalized readings in real time. Our AI strings human-written snippets together to generate hyper-personalized interpretations of planetary movements for millions of people.

We're looking for a Haskell Engineer to architect and build our Haskell backend to help tens of millions of people connect to each other and themselves – through astrology – in real, meaningful ways.

What you’ll do

  • Architect and build our Haskell backend with well-documented, easily-tested code that can gracefully scale to tens of millions of users
  • Build an elegant system that takes the infinite complexity of human language, gives our writers tools for expressive composition, and delivers relevant horoscopes to users using aggregated contextual & historical signals
  • Use machines to automate a wide variety of repetitive tasks, including some (not all) writing
  • Work extremely closely with a small, cross-functional team to negotiate, build, and ship new features with the best bang for our buck

What you'll bring

  • 3+ years of hands-on experience writing in Haskell or another functional programming language 
  • An ability to develop, scale, and maintain complex web apps on cloud infrastructure (we use AWS)
  • A disciplined approach to development, testing, documentation, and code structure in a team environment 
  • Knowledge or a willingness to learn about ML and NLP, particularly libraries like spaCy, GPT-2, and BERT, is a plus

Our technical interview process

Our interview process is divided into four phases — an initial interview with a recruiter, a secondary interview with a manager, 3–4 virtual onsite interviews (1 hour each, 2 of which are technical screens using CoderPad) with peers and cross-functional coworkers, and lastly, a meeting with our founder.

We realize technical interviews can feel challenging to prepare for, so here’s what we’re interested in seeing from you: 

  • Clean, easily-testable code that’s compiled frequently  
  • Clear communication around your decision-making process 
  • Creative and thoughtful problem-solving 
  • Self-reflection around past projects and the ability to articulate what worked, what didn’t work, and what you'd do differently now that you know the outcomes
  • Ability to partner with cross-functional coworkers outside of engineering 

We’re not interviewing for: 

  • Pure coding skills (we’re a cross-functional company and the ability to collaborate across disciplines is equally as important as coding ability)   
  • Memorization of complex algorithms or trivia (we all have access to some form of search engine and use it when we forget) 
  • Your ability to know everything (we may ask you a question you don’t know the answer to and that’s ok) 
  • “Cracking the Code” / LeetCode-type knowledge

What we offer

  • Fully covered $0 deductible healthcare (including therapy, vision, and dental) 
  • 401(k)
  • Unlimited vacation (plus a company-wide two week recharge at the end of each year) 
  • Flexible working hours
  • Readings with in-house astrologers


Co–Star deeply values diversity. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, disability status, or zodiac sign.

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