Senior Backend Developer (Kotlin)

United States Digital Space LLC; United States; Hybrid; USD 120,000 - 170,000; Full time

Benefits offered by this job

Health insurance

Remote-friendly 52 days/yr

28 days paid leave

AI tools access

English courses

Job summary

Onfy is seeking a Senior Backend Developer to own core backend systems, scale services, and drive architecture decisions. You will work across platforms and collaborate with cross‑functional teams to deliver reliable, scalable features.

Strong Kotlin/JVM skills and experience with PostgreSQL and cloud-native stacks are essential. The role emphasizes AI-enabled engineering workflows and a hybrid work model combining office presence with remote days.

Qualifications

• 5+ years of backend engineering experience in production environments.

Responsibilities

• Build and maintain a fast, reliable backend
• Own platform architecture and scalability
• Collaborate across teams to deliver robust features
• Apply AI tools to improve speed, quality and decisions

Skills

Backend engineering

Kotlin

Software architecture

PostgreSQL

AI tools

English communication

Tools

Kotlin

Spring

PostgreSQL

AWS

Kubernetes

Redis

Spark

Scala

Job description

We are Onfy - a German pharmacy marketplace founded in 2021. We are on a mission to constantly find new and innovative ways to support your health online. We empower our customers to take their health into their own hands by providing an easy, convenient and affordable experience.

Our website www.onfy.de (http://www.onfy.de) launched in November 2021, and since then it has developed into an online platform that offers consumers the unique ability to order and to receive health products from several pharmacies at once with low prices and fast delivery.

We are an agile, rapidly growing team of forward thinkers, and we believe in people who want to change the world of health for the better using the latest technology available.

Onfy is one of the key businesses of the company, an international tech-centric group of e-commerce companies that was founded in 2016 in Latvia. the company Group also includes the following businesses: the company, a global cross-border marketplace; JoomPro, the first and only end-to-end cross-border B2B marketplace; and JoomPulse, an AI analytics tool for Mercado Livre sellers. the company Group has offices in Latvia, China, Germany, and Brazil, with its headquarters in Lisbon, Portugal. We work as one international team, sharing knowledge and collaborating across countries, businesses and products.

We continue to evolve our product experience, making it more advanced, reliable, and engaging for users. We are looking for a Senior Backend Developer to join the Onfy team - someone with deep backend expertise who can own complex technical areas, make strong architectural decisions, and actively contribute to product discussions.

The main focus of the role is backend development. At the same time, we value T-shaped engineers. We expect the person in this role to be interested in working across platform boundaries and growing beyond frontend when it brings value to the product. We actively use AI in our engineering workflows and welcome candidates who thoughtfully apply AI tools to improve development speed, quality, and decision-making.

Tech stack: Kotlin, Spring, PostgreSQL, AWS, Kubernetes, Redis, Spark, Scala

Responsibilities

• We're hiring a Senior Backend Engineer to build and maintain a fast, reliable backend, solve scaling challenges, and own platform architecture

Requirements

• 5+ years of backend engineering experience in production environments
• 3+ years of recent experience with Kotlin or another JVM language
• Strong software architecture skills
• Relational DBMS expertise (PostgreSQL schema design \& safe migrations)
• Proven track record in customer-facing product development
• Experience with AI tools and modern AI practices
• Strong written and spoken English

Preferred

• Experience as a tech lead or engineering team lead
• AWS / Kubernetes experience
• Observability mindset (metrics, logging)
• Experience with analytics workloads (Spark / Scala)
• Full-stack experience, especially React

We offer

• Compensation package: base salary and performance-based bonuses
• Office-first: flexible hours with a possibility to work remotely 52 days per year, and 28 days of paid annual leave
• Care \& Wellbeing: health insurance for the employees, including dental care (Barmenia Mehr Zahn 100), daily meal allowance
• AI-first approach: licenses and access to a wide range of AI tools
• Team \& Growth: collaboration with colleagues across Portugal, Brazil, Latvia and China, with opportunities for promotions, professional trainings, and English courses
• Community \& Engagement: annual team building activities, knowledge-sharing workshops, and a strong sense of team work