Amazon CTO Werner Vogels says the best day of his year was when Amazon turned off its largest Oracle data warehouse

The best day of this year for Amazon's chief technology officer, Werner Vogels, was November 1.

"This was the moment when we switched off one of the world's largest, if not the largest, Oracle data warehouse and moved it over to Redshift," Amazon's own data warehouse, Vogels said Thursday on stage at Amazon Web Services' annual conference.

CNBC previously reported that Amazon planned to move off Oracle's databases completely by 2020.

Oracle's founder and CTO, Larry Ellison, scoffed at the idea, as Amazon has spent millions on Oracle databases this year.

"It's kind of embarrassing when Amazon uses Oracle but they want you to use Aurora and Redshift," Ellison said in August. "They've had 10 years to get off Oracle, and they're still on Oracle."

In early November, the CEO of AWS, Andy Jassy, tweeted that Amazon's consumer business had turned off its Oracle data warehouse, adding that the plan was to have 88% of its Oracle databases moved to Amazon's own by the end of the year.

Read more: Amazon Web Services CEO Andy Jassy roasted Larry Ellison by turning the Oracle founder into a cartoon-like face peeking over a wall

In the past six months, Redshift has become 3.5 times faster, Vogels said, adding that "there have been enormous improvements in real-world workloads."