Rishi Dhanaraj provides us with some lessons learned from implementing Kafka Streams to read data from Cassandra and Mongo and write into Mongo:
This Python script ran on a single machine, and is from the early days of the company. However, this script didn’t scale since it cannot run in a distributed manner. As a result, this Python job ends up flapping—crashing and restarting regularly in production depending on the load it needs to process.
Second, the Python script puts read pressure on MongoDB and Cassandra, because it has to query the databases for each batch of walk-ins and Zenreach Messages. MongoDB and Cassandra are our primary databases for serving customer read queries. So we wanted to remove the additional read pressure added by this job, which currently competes for resources with our customers.
For these reasons, we wanted to move to a streaming solution—specifically, Kafka Streams. We already switched to Kafka Streams for walk-in detection, which my teammate Eugen Feller explained in a previous post.
Click through for a review of the architecture and some tips if you want to do this yourself.