We are using Phoenix in production at a multinational retailer that handles millions of transactions per month. So far it has been a fantastic decision and an absolute pleasure. It’s the most reliable part of the stack in terms of uptime and speed. It’s also cheap to run and maintain. We’re migrating chunks of our ERP (extremely complex system built around SAP) to Phoenix, and the results have been consistently positive.

Although, the one thing I miss from working with Rails in the larger ecosystem.

If you have to deal with MongoDB, then you are better off with NodeJS, mainly because the driver for MongoDB is official (meaning it is made by MongoDB themselves).

Elixir does have a community driver, but it pales in comparison to the NodeJs one. We used the Elixir driver for a while but its performance was so abismal we were forced to integrate our Elixir stack with NodeJS just for the MongoDB drivers to get the performance we needed.

If however, you want GraphQL, then both Elixir and Node are good options. There is even a GraphQL book for Elixir in case you want to check it out:

Apart from the learning curve of understanding a framework, I’ve not run into any problems using Phoenix as an API server (both Rest and GraphQL through Absinthe) for iOS and Android applications.

When the Phoenix server is making a direct response to an query we see response times that are measurably faster than Node, but not perceptible at the human/UI level. In much of our usage, however, the Phoenix or Node application is acting as an intermediary (a middle-tier) to back-end systems whose API calls dominate the execution time.

One thing with Elixir and Phoenix that seems to catch folks by surprise is the unique deployment options. If you have a deployment pipeline in place for Node entities, you will likely have to explore the Elixir deployment options and change that pipeline for Elixir. It’s not overwhelming by any stretch of the imagination, but lots of folks come here with questions and remarking on how it was not as straightforward as they thought.