株式会社Spider LabsのSENIOR SOFTWARE ENGINEER - Tokyo (JP) / Lisbon (PT) Officesの求人

Job Description
As a Senior Software Engineer, you are a high-impact individual contributor responsible for solving meaningful customer problems through secure, scalable software. You take end-to-end ownership of complex initiatives
— from understanding the problem and its customer impact, through design and implementation, to validation in production and real-world adoption.

We hold a high bar for engineering excellence
— including code quality, system design, security, reliability, and operational maturity — and consider this a baseline expectation for the role. Meeting this bar is necessary, but not sufficient. Senior engineers are evaluated on the outcomes their work creates for customers and the business, not just on technical sophistication.

This is not a role focused on writing code in isolation. Engineering exists to deliver customer value. Technical decisions must balance system health with delivery speed, usability, and impact. Senior engineers are expected to exercise judgment, reason about trade-offs, and prioritize results over technical purity.

You will work hands-on across the full development lifecycle, contribute to architectural discussions, and collaborate closely with product, security, and go-to-market teams.
In many situations, senior engineers are expected to act as feature-level owners: clarifying ambiguous requirements, modeling solutions from the customer’s perspective, validating assumptions, and ensuring solutions work in real-world conditions.

Key Responsibilities

• Customer & Product Impact
  Own features end-to-end, from problem understanding and solution design through release, validation, adoption, and measurable impact.
  Translate ambiguous customer and business needs into pragmatic, high-quality technical solutions.
  Make prioritization decisions by explicitly weighing customer value, risk, opportunity cost, and time-to-impact.
  Ensure features are usable and valuable in real-world scenarios by contributing to documentation, examples, demos, and validation with real customer data.
  Monitor outcomes after release and iterate based on feedback, metrics, and operational signals.
• Technical Execution & System Quality
  Design, implement, and maintain secure, scalable, and reliable systems as a foundation for customer and business impact.
  Solve complex technical problems hands-on, improving architecture, performance, observability, and long-term maintainability.
  Make sound technical decisions that balance correctness, simplicity, and future evolution while avoiding unnecessary complexity.
  Apply strong engineering fundamentals, including secure coding, testing, and performance optimization in production environments.
  Use modern development tools and practices to improve delivery speed and quality.
• Collaboration, Ownership & Engineering Leadership
  Raise the engineering bar through code reviews, design discussions, and collaborative problem-solving.
  Communicate technical concepts, trade-offs, and risks clearly to both technical and non-technical stakeholders.
  Take ownership of outcomes, not just tasks
  — proactively identifying risks, gaps, and improvement opportunities.
  Contribute to continuous improvement of engineering practices, workflows, and tooling with a focus on enabling impact.
  Model pragmatic, customer-driven engineering behavior in day-to-day work.
  We value engineers who believe in continuous improvement and are willing to step outside their comfort zone to improve both delivery speed and quality. Successful candidates are confident in their technical skills, pragmatic in their decision-making, and care deeply about reliability, security, and code quality
  — while being equally motivated by seeing their work adopted by customers and making a measurable impact. This is a low-drama, high-trust environment where ownership, clarity, and impact matter more than technical heroics.
  How We Define “Done”
  For us, success goes beyond shipping code. “Done” is a progression:
  released → validated → adopted → impactful
  Senior engineers are expected to own features through all of these stages
  — from implementation and release, through real-world validation, to customer adoption and measurable impact. This includes contributing to documentation, examples, demos, instrumentation, and follow-up improvements based on customer feedback and observed usage.
  Engineers who consider their work complete at release time will likely find this role frustrating.

• Several years(5-7 years) of hands-on experience building and operating production systems.
• Strong software engineering fundamentals and experience applying modern development practices.
• Proven experience owning features or systems beyond initial delivery, including validation, iteration, and real-world usage.
• Experience with cloud platforms such as AWS or GCP and modern DevOps practices.
• Experience with modern Web Development and JavaScript frameworks (e.g. Vue.js).
• Strong understanding of secure coding, scalability, and performance optimization.
• Sound engineering judgment and the ability to reason about trade-offs in complex technical and product contexts.
• Strong communication skills and professional proficiency in English※
  ※ For candidates based in Japan, business-level Japanese proficiency (JLPT N3 or higher) is required.

• Experience with Elixir, Erlang, Ruby on Rails, Python/Django, or Scala/Play Framework.
• Experience in ad-tech or fraud prevention domains.
• Familiarity with big-data technologies such as BigQuery or ClickHouse.
• Experience using AI-powered development tools (e.g. code assistants, automated testing, or debugging tools) to improve productivity, code quality, or problem-solving is a plus.
• Japanese language proficiency is a plus.