The QA team employed a rigorous testing process to ensure a smooth migration from CouchDB to Elasticsearch. They relied heavily on automated and performance testing tools, including tests written in Ruby and run through Jenkins, as well as UI checks using Selenium. The team also used Gattling and JMeter for stress and performance testing. After completing automated testing on staging, the QA team performed manual testing to verify everything was in place and nothing got missed by automated tests. Despite an initial issue with data loss under heavy load, the team was able to identify and fix the problem, deploy again, and successfully migrate to Elasticsearch without significant issues. The success of this deployment is attributed to meticulous planning and execution by the QA team, as well as the use of testing tools to detect and handle minor setbacks.