Backend Engineer · Senior · Transition to Go · Saily

📍 Poland

PLN 288,000-400,800 per year

SENIOR

✅ Hybrid

Tech Stack
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1-2 — basic awareness. Minimal hands-on experience, and a rudimentary understanding of the technology's purpose;

3-6 — daily use. Comfortable and regular usage, capable of handling common tasks and challenges related to the technology;

7-9 — you are an expert, you can teach others, you know all the pitfalls and tricks;

10 — exceptional knowledge, comprehensive understanding, and adeptness in all aspects of the technology, including advanced problem-solving. Think twice before claiming or demanding such level.

AI @ 6 API @ 4 AWS Cassandra @ 4 Experimentation Java @ 6 Kafka @ 4 Kotlin @ 6 Kubernetes @ 1 Microservices MySQL @ 4 NoSQL @ 4 PHP @ 4 PostgreSQL @ 4 Python @ 4 Redis @ 4 SQL @ 4

Details

At Saily, you will help build a new eSIM product that provides secure mobile data in more than 200 destinations. The role is part of an AI-native Product Engineering culture, where engineers solve customer problems end to end and use AI agents for repeatable development tasks.

Responsibilities

Build a sophisticated new microservices system for the eSIM product.
Create features supporting multidimensional personalization, A/B experimentation, and analytics.
Develop and maintain a high-quality codebase.
Continuously improve code quality and performance.
Mentor colleagues on development best practices and provide technical guidance.
Influence the overall vision and long-term goals of the team.
Perform research and development operations when required.
Use AI agents for specifications, coding, analysis, testing, and iteration.
Work as part of a cross-functional team and support smooth communication between team members.
Collaborate with engineering, product, and design professionals from other teams.

Requirements

More than 4 years of backend development experience.
Experience with one or more backend languages: PHP, Python, C#/.NET, Java, or Kotlin.
Strong system design knowledge, including understanding which patterns to use, when, and why.
Experience with Kubernetes and microservice architecture is a plus.
Experience with SQL databases such as MySQL and PostgreSQL.
Experience with NoSQL solutions such as Cassandra and Redis.
Previous experience with Kafka.
Passion for building easy-to-use and understandable APIs.
Strong product mindset, with a focus on problems, outcomes, and impact rather than only tickets or tasks.
Curiosity about AI and enthusiasm for working with AI agents.

Tools

Go
MySQL
Kafka
Kubernetes
AWS
Redis
AI tools such as Copilot and Cursor

Benefits

Online and in-person training, access to Coursera and Skillshare, mentorship, and internal career opportunities.
Additional vacation days, sick leave, special-occasion leave, and parenting leave.
Premium private health insurance available in Lithuania and Poland.
Subscriptions to Calm, Headspace, and Mindletic, plus resilience and mindfulness training and mental health events.
In-house gyms, Multisport and Urban Sport cards, online workouts, and physical well-being consultations.
Company workations abroad.
The ability to work from different locations.
Gifts for birthdays, work anniversaries, weddings, and new family members.
Summer camps for children and flexible working arrangements for parents.
Team-building activities and company events.
Access to the Vilnius headquarters, including silent rooms, gyms, a game room, a music room, and a coffee bar.