Software Engineer, Foundations

Mosaic.tech; San Francisco (CA); On-site; USD 215,000 - 270,000; Full time

Job summary

Hex is hiring a Senior Backend Software Engineer to design and evolve core systems used across our platform. You will own APIs, realtime transport, data access frameworks, and job orchestration, leaning into scalable, secure backend infrastructure.

You'll collaborate with product teams to turn recurring needs into shared abstractions, drive architectural direction, and mentor others while improving reliability, performance, and observability.

Qualifications

• 5+ years of professional software engineering experience with a strong backend focus.
• Experience with Typescript/Node.js and SQL.
• Experience building and maintaining shared backend systems or frameworks used by multiple teams.
• Strong understanding of API design, distributed systems, and asynchronous workflows.
• Experience with relational databases and data modeling at scale.

Responsibilities

• Design and build backend frameworks and services used across the company.
• Own and evolve critical shared systems, including APIs, realtime transport, and job orchestration.
• Improve reliability, performance, observability, and security of foundational backend infrastructure.
• Partner with product teams to turn recurring needs into shared abstractions.
• Lead technical design discussions and help set architectural direction.
• Drive refactors, migrations, and system upgrades that reduce long-term complexity.
• Improve internal tooling to support debugging, operations, and customer-facing workflows.
• Mentor other engineers and contribute to strong engineering standards and practices.

Skills

5+ years background

Typescript/Node.js

SQL

APIs

Distributed systems

Relational databases

AWS

Communication

Tools

GraphQL

WebSockets

BullMQ

Temporal

Postgres

Redis

Kubernetes

Terraform

Helm

Express

Job description

About the team

The Foundations team builds and evolves the application-level infrastructure that powers Hex. We own the shared backend systems, frameworks, and primitives that other teams depend on—helping the company move faster while maintaining reliability, performance, and security.

Our work spans APIs, realtime transport, storage frameworks, background processing, and internal tooling. Rather than shipping isolated features, we focus on creating durable systems that scale with the company and make product development easier for everyone.

About the role

We’re looking for a Senior Backend Software Engineer to help design, maintain, and evolve the core systems used across Hex. This role is centered on backend architecture and shared infrastructure, with responsibility for APIs, realtime communication, data access frameworks, job orchestration, and internal admin tooling.

You’ll work closely with product engineering teams to understand their needs, then turn common patterns into robust, reusable systems. You’ll help define standards, influence architecture, and raise the quality bar across the backend.

Frontend experience is helpful for understanding end-to-end workflows, but this role is primarily backend-focused.

Core Contributions

You will help contribute to and evolve several foundational areas, including:

APIs

• GraphQL(schema design, performance, developer ergonomics)
• Authentication & authorization(security, scalability, correctness)
• Multiplayer & collaboration APIs(realtime state, concurrency)

Transport

• WebSockets and realtime communication infrastructure

Storage Frameworks

• Postgres(schema design, query optimization, migrations)
• S3, DynamoDB, Redis

Job & Workflow Systems

• BullMQ and background job processing
• Temporal or similar workflow orchestration systems

Internal Tooling

• Internal admin tools for debugging, operations, and customer support

What You'll Do

• Design and build backend frameworks and services used across the company
• Own and evolve critical shared systems, including APIs, realtime transport, and job orchestration
• Improve reliability, performance, observability, and security of foundational backend infrastructure
• Partner with product teams to turn recurring needs into shared abstractions
• Lead technical design discussions and help set architectural direction
• Drive refactors, migrations, and system upgrades that reduce long-term complexity
• Improve internal tooling to support debugging, operations, and customer-facing workflows
• Mentor other engineers and contribute to strong engineering standards and practices

What we're looking for

• 5+ years of professional software engineering experience with a strong backend focus
• Experience working with Typescript/Node.js and SQL
• Experience building and maintaining shared backend systems or frameworks used by multiple teams
• Strong understanding of API design, distributed systems, and asynchronous workflows
• Experience working with relational databases and data modeling at scale
• Familiarity with background job systems, queues, or workflow orchestration tools
• Comfort operating and evolving production systems over time
• Experience with cloud infrastructure (AWS preferred)
• Strong communication skills and a collaborative, leverage-oriented mindset

Bonus Points

• Experience with Python
• Hands‑on experience with GraphQL, WebSockets, BullMQ, or Temporal
• Familiarity with observability tooling (metrics, tracing, logging)
• Background in data platforms, developer tools, or collaborative systems
• Experience with frontend technologies (e.g. React, TypeScript) for end‑to‑end context
• Open-source contributions, especially in backend or infrastructure projects

Our stack

Our product is a web-based notebook and app authoring platform. Our frontend is built with Typescript and React, using a combination of Apollo GraphQL and Redux for managing application state and data. On the backend, we also use Typescript to power an Express/Apollo GraphQL server that interacts with Postgres, Redis, and Kubernetes to manage our database and Python kernels. Our backend is tightly integrated with our infrastructure and CI/CD, where we use a combination of Terraform, Helm, and AWS to deploy and maintain our stack.

In addition to our unique culture, Hex proudly offers a competitive total rewards package, including but not limited to, market‑bench salary & equity, comprehensive health benefits, and flexible paid time off.

The salary range for this role is: $215,000 - $270,000

The salary range shown may be a reflection of additional factors such as geographical location and skill ranges/levels we’re open to. Placement in the salary range will be decided upon completion of the interview process, taking into account factors like leaving room for growth, internal fairness & parity, your demonstrated skills, and the depth of your experience. Our Recruiting team will be able to provide more details during the interview process.