Backend Engineer Senior

At Saily, we're removing the hassle of staying connected while traveling — no roaming fees, no plastic SIM cards, just lightning-fast, secure mobile data in 200+ destinations. Millions of paying customers trust us, and hundreds of thousands of travelers browse Saily at any given moment.
We're not looking for someone to close tickets. We're looking for a builder — someone who has shipped products real people use, felt the pain of a 2 AM incident on something they care about, and gets a kick out of seeing a metric move because of something they built.

Our Culture: AI-native Product Engineering

• The Engineer is the builder — responsible for solving customer problems end-to-end, from idea to production

• AI Agents are the enablers — they write most of the code and handle repeatable tasks, so you maximize your impact

• Everyone makes Saily more effective — you suggest what to delegate to agents, then implement the changes

• Curiosity, learning, and sharing are everyone's job

• The customer — a traveler on a comfortable, connected, hassle-free journey — never leaves our focus

We value growth over comfort, contribution over hierarchy, and impact over process. We give sharp people context, autonomy, and AI as their multiplier — and expect their best work in return.
Main Responsibilities

• Own product features end-to-end: from shaping the idea with Product and Design to shipping, measuring, and iterating

• Build features supporting multi-dimensional personalization, A/B experimentation, and analytics

• Make technical decisions with a product lens — you'll know the "why" behind every "what"

• Develop and maintain a high-quality, high-performance codebase in Go

• Mentor colleagues and raise the bar on engineering best practices

• Influence your team's vision and long-range goals — your opinion on what we build matters as much as how

• Run R&D spikes when the path forward isn't obvious

• Collaborate across engineering, product, and design in a cross-functional team

Requirements

• 5+ years of backend development experience, with strong skills in Python, PHP, Ruby, or similar — and readiness to work in Go daily

• Product company experience, ideally startup or scale-up — you've worked where speed, ambiguity, and ownership are the norm, not the exception

• B2C experience strongly preferred — you understand what it means to build for millions of users you'll never meet, where small UX details and performance directly hit revenue and retention

• Solid system design skills: you know which patterns to use, when, and why

• Experience with SQL (MySQL, PostgreSQL) and NoSQL (Redis, Cassandra) solutions

• Experience with Kafka or similar event-driven systems

• Passion for building APIs that are easy to use and simple to understand

• A collaborative mindset — you love discussing, rethinking, and redesigning ideas toward shared success

Bonus Points

• You've built your own product — a side project, a startup (successful or not), an indie app, anything you took from zero to real users. We find that people who've carried a product themselves think differently: they obsess over the user, they ship, they own outcomes. If that's you, tell us about it — it matters more to us than logos on your CV

• Experience with K8s and microservice architecture

• A track record of experiments shipped, hypotheses tested, and impact measured (not just features delivered)

• Comfort working AI-native: Claude Code, Codex, Cursor — you see AI as a multiplier, not a threat

Don’t quite match every requirement?
Our technical bar is high, but we’d rather help you reach it than lose a great person over it. If your mindset and technical potential make an impression, but your Go skills aren’t quite there yet, we may invite you to the GO Masterclass: fully funded access to the Three Dots Labs’ Golang training platform. Level up, come back, and interview again — we’d love to see you grow into this role!

Tools You Will Use

• Backend: Go, MySQL, Kafka, Docker, Kubernetes, AWS, Redis

• Frontend: Next.js, React, TypeScript, GraphQL, Tailwind CSS, Cloudflare Workers

• iOS: SwiftUI, Xcode, Combine, SPM, MVVM

• Android: Kotlin, Hilt, Coroutines, Jetpack Compose, MVVM

• AI tools: Claude Code, OpenAI Codex, OpenCode, Cursor

What We Offer

• Sharpen your edge: training, mentorship, and room to grow — always.

• Take the time you need: extra vacation days, sick days, and time off when life calls.

• Get premium healthcare: private health insurance in Lithuania and Poland — fully covered.

• Protect your peace: enjoy free subscriptions to Calm, Headspace, and Mindletic, and our own resilience and mindfulness trainings.

• Own your fitness: in-house gyms, sport cards, online workouts, and personal guidance — on us.

• Pack your bags for workation: experience our company-wide trip abroad to the fullest.

• Work from anywhere: work from wherever keeps you in the zone.

• Celebrate your milestones: birthdays, weddings, and new family members — all deserve a gift.

• Parent with ease: children’s summer camps and flexibility around the schedule — because parenting never pauses.

• Join the party: team building and company events people talk about for months.

• Unlock Cyber City: coffee bar, open gyms, kids’ room, music room, massage chairs — our Vilnius HQ is yours to enjoy.

Kindly refer to our Privacy Notice for Recruitment Candidates for comprehensive information regarding our data handling procedures throughout recruitment processes.

We expect all candidates to provide accurate and complete information during the recruitment process. While limited use of AI tools to refine application materials is acceptable, candidates remain fully responsible for ensuring that their submissions reflect their own qualifications, skills, and experience. Any failure to do so may negatively affect participation in the recruitment process. If broader AI assistance is allowed for a particular role or stage, we’ll let you know in advance.

By submitting your application, you acknowledge that it may be processed using automated tools for evaluation purposes. As part of our recruitment process, we may use an AI-based application review tool to help assess applications based on skills and experience relevant to the role. This technology is used to support - not replace - human decision-making, and every application is ultimately reviewed by a recruiter.

If you would like more information about how AI is used in this process or wish to exercise your rights under applicable data privacy laws, please contact us at [email protected]. Should you prefer to opt out of the automated evaluation, please submit your application directly to [email protected].