Job Description
Digital advertising operates at a massive scale and faces increasingly sophisticated threats. At Spider AF, we build systems that detect and prevent these threats in real time — protecting businesses and customers in production environments where reliability, performance, and security matter every day.

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, much beyond writing high-quality code.

Because our systems operate in live production environments where engineering decisions directly affect real customers, we hold a high bar for engineering excellence - including code quality, system design, security, reliability, and operational maturity - and consider these baseline expectations 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.
Engineering at Spider AF is deeply connected to customer outcomes. 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 that operate in production environments under strict reliability and performance expectations.

• 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 (CI/CD, automated testing, monitoring) 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 believe strong engineers thrive when given real ownership and clear expectations. 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 — rather than at customer adoption and measurable impact — will likely find this role frustrating.

What Success Looks Like in the First 6 Months

• In your first months, you will be expected to move beyond onboarding and begin delivering meaningful impact. While exact projects vary, a successful start typically includes:
  Taking ownership of a production feature and delivering it through release, validation, and early adoption.

• Contributing to improvements in system reliability, performance, or maintainability within an existing service.

• Contributing to architectural discussions and contributing thoughtful trade-offs grounded in customer and operational impact.

• Engaging directly with product and stakeholders to clarify requirements and validate assumptions.

• By the six-month mark, you should be operating with increasing autonomy, making sound decisions that balance technical quality with measurable customer value.

• Several years (5–7+) of hands-on experience building and operating production systems.

• Strong software engineering fundamentals and experience applying modern development practices in real-world production environments.

• Proven experience owning features or systems beyond initial delivery, including validation, iteration, and measurable real-world usage.

• Experience operating production systems on cloud platforms such as AWS or GCP, including CI/CD, monitoring, and incident response practices.

• Experience with modern Web development and JavaScript frameworks (e.g., Vue.js), contributing to user-facing functionality.

• Strong understanding of secure coding, scalability, reliability, 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 in production environments.

• Experience in ad-tech, fraud prevention, or other high-volume data processing domains.

• Familiarity with big-data technologies such as BigQuery or ClickHouse.

• Experience using AI-powered development tools (e.g., code assistants, automated testing, debugging tools) to improve productivity and code quality.