Senior Fullstack Mobile Engineer (KMP/Java) K/M

Integral Solutions - Data & AI; Województwo mazowieckie; Remote; PLN 344,000 - 369,000; Full time

Job summary

Integral Solutions - Data & AI is seeking a Senior Fullstack Mobile Engineer (KMP/Java) to join as a remote role from Poland. You will contribute across the full stack, from mobile apps built with Kotlin and Kotlin Multiplatform to backend services using Java and Spring Boot.

You will take ownership of features end-to-end, collaborating with cross-functional teams to deliver scalable, secure, and high-quality digital financial products used by millions of customers.

Qualifications

• Experience in mobile apps development with Kotlin or Kotlin Multiplatform.
• Strong knowledge of Android or iOS architectures.
• Production-grade Kotlin applications experience.
• Backend experience with Java, Spring Boot and microservices.
• Experience with CI/CD and production environments.
• Ability to own features end-to-end.

Responsibilities

• Develop shared business logic across mobile platforms using Kotlin Multiplatform (KMP).
• Design and build backend services and APIs using Java, Kotlin, and Spring Boot.
• Build and enhance customer-facing mobile features used by real customers every day.
• Work with cloud services, CI/CD, observability, monitoring, and production systems.
• Improve scalability, reliability, performance, security, and user experience.
• Collaborate closely with product, design, architecture, security, and platform teams.
• Drive engineering excellence through technical leadership, mentoring, and best practices.

Skills

Kotlin

Kotlin Multiplatform

Android architecture

iOS architecture

Java/Spring Boot

CI/CD

APIs / Microservices

Job description

Job title: Senior Fullstack Mobile Engineer (KMP/Java) K/M

Location: Remote anywhere from Poland

Work mode: Remote

Type of cooperation: B2B contract

Salary range: B2B: 7000 - 7500 Euro/month - netto

About The Company/project

• Build the Next Generation of Digital Financial Products Join a team building one of the largest digital financial platforms in its market, serving millions of customers and processing millions of real-time financial transactions every month.

This is a unique opportunity to work on products that have become a natural part of users' daily lives, delivering fast, secure, and seamless financial experiences at scale. As a Senior KMP Engineer, you will contribute across the entire technology stack - from customer-facing mobile applications and shared cross-platform logic to backend services, APIs, cloud infrastructure, and large-scale production systems.

Our core technology stack includes Kotlin, Kotlin Multiplatform (KMP), Java, and Spring Boot.

Why Join Us?

• Build products used daily by millions of customers.
• Work on large-scale, business-critical systems processing millions of real-time financial transactions every month.
• Take full end-to-end ownership of features, from design and implementation to deployment and production support.
• Help shape the future of our mobile platform strategy through Kotlin Multiplatform (KMP).
• Collaborate in small, high-impact teams where engineers have real influence on technical decisions.
• Solve challenging problems across mobile development, backend services, cloud infrastructure, scalability, reliability, and security.
• Be part of an engineering culture where AI is used every day as a practical development tool, accelerating delivery and enabling engineers to focus on solving meaningful business and technical challenges.

Responsibilities

• What You’ll Do
  • Develop shared business logic across mobile platforms using Kotlin Multiplatform (KMP).
  • Design and build backend services and APIs using Java, Kotlin, and Spring Boot.
  • Build and enhance customer-facing mobile features used by real customers every day.
  • Work with cloud services, CI/CD, observability, monitoring, and production systems.
  • Improve scalability, reliability, performance, security, and user experience.
  • Collaborate closely with product, design, architecture, security, and platform teams.
  • Drive engineering excellence through technical leadership, mentoring, and best practices.

You Are An Ideal Candidate If You Have

What We're Looking For

• Strong commercial experience in mobile application development with Kotlin or Kotlin Multiplatform.
• Deep understanding of modern Android OR iOS architectures and software design principles.
• Strong Kotlin skills and experience building high-quality, production-grade applications.
• Some backend development experience with Java, Spring Boot, APIs, and microservices
• Familiarity with distributed systems, event-driven architectures, and modern engineering practices.
• Experience with CI/CD, automated testing, and production environments.
• Ability to take end-to-end ownership of features from design through production.
• Strong communication and collaboration skills.

Nice To Have

• Experience in fintech, banking, payments, or other regulated industries.
• Experience with Apple Pay, Google Pay, wallet technologies, or payment integrations.
• Experience building modular mobile applications, SDKs, or shared libraries.
• Experience with observability, performance optimization, and production incident analysis.