Full-Stack Backend Engineer — Marketplace & Payments

Kongi; Northern (KY); On-site; USD 90,000 - 150,000; Full time

Job summary

Kongi is hiring a full-stack engineer with a backend-centric focus to build and scale the marketplace. You’ll own the catalog, search, recommendations, checkout, and ads infrastructure, shipping features from API to app and web within weeks.

You will drive reliability, performance, and money-handling correctness, while collaborating with founders and small teams across the product. Expect rapid iteration and end-to-end ownership.

Qualifications

• 4+ years building backend systems for a product people use, or 2+ as an early engineer at a startup.
• Fluency in at least one major programming language.
• Real database fluency: schema design, constraints and transactions, migrations as files, indexes you can explain.
• Care with money and correctness: idempotency, retries and reconciling against a payment provider.
• Track record of owning things end to end at a startup or small team, not just a slice of a big codebase.
• Product instinct: you notice what a change means for shoppers and brands, not just the code.
• Clear communication: you name tradeoffs, ask questions and stay low-ego when corrected.

Responsibilities

• Build the marketplace end to end across API, app and web.
• Keep the catalog in sync with brands' stores: prices, stock, options and photos.
• Build checkout, payments, refunds and the credit ledger for accuracy.
• Improve search and recommendations with embeddings and ranking.
• Make every screen feel instant, with caching and fast loads.
• Own deploys, tests and monitoring to ship daily without breaking things.
• Keep ads auctions and budgets accurate and hard to game.

Skills

Backend development

API design

Database design

Distributed systems

Code quality

Education

Bachelor's degree in CS

Tools

PostgreSQL

Redis

Git

Docker

Job description

Kongi is hiring a full-stack engineer with a backend-centric focus to build and scale the marketplace. You’ll own the catalog, search, recommendations, checkout, and ads infrastructure, shipping features from API to app and web within weeks.

You will drive reliability, performance, and money-handling correctness, while collaborating with founders and small teams across the product. Expect rapid iteration and end-to-end ownership.