Recalculate historical data using Apache Beam

I have an Apache Beam streaming project that calculates data and writes it to the database, what is the best way to reprocess all historical records after a bug fix or after changing the way it processes data without a big delay?

It is quite application dependent.

For example, a straightforward approach if you are using Kafka (and all data is in there):

• Stop and relaunch the job (or if you want no downtime at all, launch another job while the other keeps running) without using a savepoint:
  • Use a different Kafka consumer group to not mess with the existing pipeline
  • Set a new database as output to build its contents from scratch
  • Scale up the job so it finishes to reprocess as fast as possible
• Switch the old database with the new one atomically
• Scale back down the job