Senior Backend Engineer (Kotlin / Java)

Fourthwall is a product company serving creatives, brands, and startups who run shops, memberships, and donations with their own domain and data. Among clients are MKBHD, Y Combinator, and the Smithsonian. The company has offices in Los Angeles and Poznań and is backed by investors including Lightspeed and Initialized Capital.

• Production experience in Kotlin or Java on a Spring backend.
• Strong SQL skills and understanding of what SQL queries run and ORM abstractions.
• Knowledge of proper error handling, including use of return types like Either or Kotlin Result.
• Experience integrating at least one third-party API end to end with attention to contract, retries, idempotency, and error handling.
• Understand performance and failure modes of queries, HTTP calls, or background jobs.
• Experience shipping features and measuring their impact on users or revenue.
• Experience making deliberate design tradeoffs when requirements change.
• Ability to quickly get up to speed on work outside your normal domain, such as data pulls or Terraform modules.
• Clear written English.

• Join the backend on-call rotation.
• Maintain and develop the Kotlin backend service handling payments, refunds, payouts, and tax.
• Collaborate in feature planning, building, and rollout cycles.
• Work with coding agents and own the code you merge.
• Troubleshoot production issues and communicate with support and growth teams.

The controller of personal data is Fourthwall, Inc. They process personal data for recruitment purposes based on legal grounds including Labour Code and GDPR. Data provision required by law is mandatory; other data provision is voluntary. Personal data may be stored up to 24 months with consent. Candidates have rights to access, rectify, erase, restrict, port data, object and lodge complaints.