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The inside sales CRM of choice for SMBs

About Us

At Close, we're building the sales communication platform of the future. With our roots as the very first sales CRM to include built-in calling, we're leading the industry toward eliminating manual processes and helping companies to close more deals (faster). Since our founding in 2013, we've grown to become a profitable, 100% globally distributed team of 90+ high-performing, happy people that are dedicated to building a product our customers love.

Our Tech Stack


Our backend tech stack currently consists primarily of Python Flask web apps with our TaskTiger scheduler handling many of the backend asynchronous task processing chores. Our data stores include MongoDB, PostgreSQL, Elasticsearch, and Redis. The underlying infrastructure runs on AWS using a combination of managed services like EKS, MSK, RDS and ElasticCache and non-managed services running on EC2 instances. All of our compute runs through CI/CD pipelines that build Docker images, run automated tests and deploy to our Kubernetes clusters.

Our backend primarily serves a well-documented public API and GraphQL endpoint that our front-end JavaScript app consumes. Our infrastructure is heavily automated using Terraform, Ansible and other AWS tools.


Our app’s frontend is a single-page TypeScript web app mostly written in React (originally built with Backbone.js). Our mobile app is built using React Native. We bundle with Webpack and target only modern browsers. We test with Jest, React Testing Library, and Playwright. Our UI updates in near real-time and is written in LESS/CSS (with flexbox and grid layout) using CSS modules and takes advantage of fun technologies like Websockets and WebRTC.

We care about performance (e.g. route-based code splitting), maintainability, and testability of our frontend code. Our product development process is inspired by Shape Up. We sweat the UI/UX details and work collaboratively with the Product team throughout the design process. This means diving into lo-fi wireframes, and communicating continuously when those ideas are brought to life using Figma and code.

More about us

  • The Making of Close – Our behind-the-scenes Product & Engineering blog
  • Jobs at Close – We're hiring for our 100% remote team
  • About Us – Learn about us
  • API – Our REST API for developers wanting to integrate with Close


  1. tasktiger tasktiger Public

    Python task queue using Redis

    Python 1.4k 81

  2. react-custom-scroller react-custom-scroller Public

    Super simple React component for creating a custom scrollbar cross-browser and cross-devices.

    JavaScript 35 8

  3. ciso8601 ciso8601 Public

    Fast ISO8601 date time parser for Python written in C

    Python 557 41

  4. closeio-api closeio-api Public

    Python API Client for Close

    Python 65 47

  5. cleancat cleancat Public

    Validation and serialization library for Python designed to be used with JSON REST frameworks

    Python 51 7

  6. use-infinite-scroll use-infinite-scroll Public

    Super simple React hook for creating an infinite scroll experience based on the IntersectionObserver API

    JavaScript 38 8


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