Backend Engineer - Application Foundation

About Us

At Sales Marker, our mission is to create a world where all people and companies can challenge themselves beyond existing boundaries. We’re one of the fastest growing start-ups in Japan and we’re growing at a speed that is twice as fast as Unicorn startups. By using our product, sales teams can improve their work efficiency by 3 times. We have achieved over 900% YoY business growth rate in 2.5 years since our flagship product 「Sales Marker」 was released and we’re currently actively working on a wide range of new product portfolios.

The Team

The Common Foundation team helps engineering teams move faster by providing scalable, reliable, and reusable systems that serve as the platform for product development. The Application Foundation side focuses on building core backend services and APIs that reduce duplication, clarify ownership, and enable product teams to deliver sophisticated features efficiently.

We design systems that support integration at scale, with an emphasis on abstraction, reliability, and long-term maintainability.

The Role

We're looking for a Senior Backend Engineer who thrives at the intersection of architecture, execution, and business understanding.

In this role, you'll lead the design and evolution of backend systems that serve as shared infrastructure across product teams. You'll help re-architect legacy components pragmatically, shape platform-level tools, and create services that turn complex business needs into flexible technical building blocks.

What You'll Do

● Design and implement scalable backend services and APIs that support cross-team usage and reduce redundancy.
● Translate complex and evolving business requirements into modular systems with clear separation of responsibilities.
● Drive re-architecture efforts that balance delivery speed, reliability, and long-term maintainability.
● Collaborate with product teams to ensure foundation systems empower them to move fast without reinventing the wheel.
● Apply strong testing, observability and monitoring practices to ensure operational excellence.
● Work across service boundaries and repositories to design cohesive solutions.
● Guide system design discussions and mentor team members on architecture, reliability, and code quality.

Tech Stack

We use a modern, cloud-native architecture. You don’t need to be fluent in everything, but familiarity with several is highly valued:

Languages: Go (primary), TypeScript, Python

APIs: gRPC, REST, Protocol Buffers

Infrastructure: AWS (EKS, RDS, S3), Kubernetes, AWS Amplify, RDS Proxy

CI/CD & GitOps: GitHub Actions, ArgoCD

Observability: Datadog (APM, metrics, logs)

Databases: Amazon Aurora (MySQL-compatible), Vector DB, Redis

Search: OpenSearch

Realtime Communication: WebSockets, Server-Sent Events (SSE), gRPC streaming

Authentication & Identity: AWS Cognito, JWT, internal session systems

Frontend Touchpoint: React (via product teams), OpenAPI/.proto SDK generation

What We're Looking For

Required
● 5+ years of backend software engineering experience, with a track record of delivering robust, scalable systems.
● Proficient in at least one backend programming language and open to working across stacks.
● Deep understanding of API design, data modeling, distributed systems, and software abstraction principles.
● Experience working on systems used by multiple product teams or customer-facing domains.
● Familiarity with service-oriented or micro-service architectures and tooling such as gRPC, Protocol Buffers, Kubernetes, CI/CD platforms, and observability tools like Datadog.
● Ability to collaborate across backend, frontend, and infrastructure disciplines with strong communication skills.
Bonus
● Understanding of the Identity Provider (IDP) domain and security concerns such as authentication flows, token management, and session modeling.
● Experience working with modern AI agent tooling or MCP (Model Context Protocol) server architectures.
● Familiarity with frontend technologies or patterns - enabling better API design and integration.
● Exposure to multi-tenant systems, permission models, or platform product design.
● Contributions to internal developer tooling, libraries, or DX initiatives.

Why Us? **

• One of the fastest growing Saas startup in Japan with strong financial growth
• Innovative new product development and opportunity to build things from scratch.
• Plenty of leadership and career development opportunities.
• Remote-friendly & full flexible work schedules.
• Global team and English speaking environment.
• Great benefits & perks packages such as Resort Worx, Purchasing Books, Free Weekly Lunch, Offsites, etc.

Working Style
● Hybrid Work
We follow a hybrid work style, combining both office and remote work. Recommended in-office days vary by role. Even when working remotely, we maintain smooth collaboration and communication through tools like Zoom, Google Meet, and Gather.

● Flex Work
You can customize your working hours to suit your day. For business and client-facing teams, schedules are often arranged around client meetings.

● Global Environment
With team members from over 20 countries, we bring together diverse perspectives and ideas, driving projects forward across languages and cultures in an environment where English and Japanese blend naturally into daily communication.

Read More
■Career Page: https://sales-marker.jp/corporate/en/
■Culture Book: https://speakerdeck.com/salesmarker/sales-marker-culturebook-en
■YouTube: https://www.youtube.com/watch?v=Ob8Ds06zwo0