Zulip has been powered by Django since the very early days of its development with Django 1.4, back in 2012. As a reasonably mature web application with significant scale, we're at the stage in many companies' development where one starts to rip out more and more of the web framework to optimize things or just make them work the way we want. (E.g. while I was at Dropbox in early 2016, we discovered we only had about 600 lines of code left from the original Pylons framework that actually ran).

One of the things that has been really fantastic about Django is that we're still happily using it for the vast majority of code in the project, and every time Django comes out with a new release, I read the changelog and get excited about several improvements that actually make my life better. While Django has made some design decisions that I don't agree with (e.g. I'm not a fan of Django REST framework, and think it makes life more difficult), Django also makes it easy to do your own thing, which we've done to great effect (see the linked article for details on our has_request_variables framework).

Overall I think we've gotten a ton of value out of Python and Django and would recommend it to anyone starting a new full-featured web application project today.

Unlike our frontend, we chose Flask, a microframework, for our backend. We use it with Python 3 and Gunicorn.

One of the reasons was that I have significant experience with this framework. However, it also was a rather straightforward choice given that our backend almost only serves REST APIs, and that most of the work is talking to the database with SQLAlchemy .

We could have gone with something like Hug but it is kind of early. We might revisit that decision for new services later on.

We are in the process of building a modern content platform to deliver our content through various channels. We decided to go with Microservices architecture as we wanted scale. Microservice architecture style is an approach to developing an application as a suite of small independently deployable services built around specific business capabilities. You can gain modularity, extensive parallelism and cost-effective scaling by deploying services across many distributed servers. Microservices modularity facilitates independent updates/deployments, and helps to avoid single point of failure, which can help prevent large-scale outages. We also decided to use Event Driven Architecture pattern which is a popular distributed asynchronous architecture pattern used to produce highly scalable applications. The event-driven architecture is made up of highly decoupled, single-purpose event processing components that asynchronously receive and process events.

To build our #Backend capabilities we decided to use the following: 1. #Microservices - Java with Spring Boot , Node.js with ExpressJS and Python with Flask 2. #Eventsourcingframework - Amazon Kinesis , Amazon Kinesis Firehose , Amazon SNS , Amazon SQS, AWS Lambda 3. #Data - Amazon RDS , Amazon DynamoDB , Amazon S3 , MongoDB Atlas

To build #Webapps we decided to use Angular 2 with RxJS

#Devops - GitHub , Travis CI , Terraform , Docker , Serverless