How many partitions to use for a topic?

gistfile1.txt

The formula for determining the number of partitions per Kafka topic has been pretty well explored over time. 
When creating a new topic in your Kafka cluster, you should first think about your desired throughput (t) in MB/sec. 
Next, consider the producer throughput that you can achieve on a single partition (p)—this is affected by producer 
configurations but generally sits at roughly 10s of MB/sec. Finally, you need to determine the consumer throughput (c) 
you will have—this is application-dependent so you’ll have to measure it yourself. You should anticipate having at least 
max(t/p, t/c) partitions for that topic. So if you have a throughput requirement of 250 MB/sec, with a producer and 
consumer throughput of 50 MB/sec and 25 MB/sec respectively. 
Then you should use at least max(250/50, 250/25) = max(5, 10) = 10 partitions for that topic.

https://www.confluent.io/blog/5-common-pitfalls-when-using-apache-kafka/