Zero Inbox is composed of a frontend Angular 12 web app, 4 backend microservices, and a host of cloud provider tools.
Angular 
bash 
Docker 
eslint 
Express.js 
Firebase 
fontawesome 
git 
Google Analytics 
Google Cloud 
Kubernetes 
mochajs 
MongoDB 
ngx-translate 
ngrx 
node.js 
npm 
Prettier 
RabbitMQ 
redis 
rxjs 
sinon.js 
tailwindcss 
Typescript 
Ubuntu 
VSCode 
The front end is built using Angular 12. Primary libraries used are NgRX, fontawesome, tailwindcss, and RxJS. The app is designed to be mobile first and makes heavy use of the MVC design pattern. Redux is used as the primary data store and there is reactivity built throughout. The site is hosted on Netlify and CI/CD workflow is achieved using github.
The Api-Gateway is the entry point into the backend. The API gateway is built with ExpressJS and runs in a Node container on a Google Kubernetes cluster. Its primary responsibility is to handle user auth/sessions, fetching email/user data, and dispatching instructions to the other microservices. It handles auth using Googles auth API and tracks user sessions using a Redis container. Email/user data is fetched from MongoDB. Instructions to other microservices are dispatched using RabbitMQ.
The Message-Ids Controller receives instructions from the API gateway anytime a users emails need to be downloaded. It connects to the Gmail API to download message Ids that are in a users Inbox but not yet in the ZeroInbox database. It stores all of the message Ids in MongoDB and sends instructions with RabbitMQ to the Batch-Messages controller to download the email content of those new messages.
The Batch Messages Controller receives instructions from the Message Ids service via RabbitMQ anytime message content needs to be downloaded. On a users first login often 10s of thousands of messages need to be fetched and stored in MongoDB. The Batch service fetches the metadata for the messages in large chunks using batch http calls to the Gmail API.
The Actions Service is the primary service used to manipulate a users inbox. It receives instructions via RabbitMQ. It can delete messages in bulk. It can create labels, label messages, and move them out of the inbox. It can also create filters to direct messages from a specific sender to a label in the future. Lastly, it can craft and send unsubscribe emails on a users behalf to take them off of a mailing list.
Zero Rabbit is a library that I built specifically for this project. The alternative options were insufficient for my use case. Beyond being a wrapper to the core amqplib, it tracks and manages "channels" within the RabbitMQ connection. Channels are used for establishing and reading from multiple queues over a single connection.