A report from CNBC, which obtained an internal Amazon report, said the incident showed that Oracle's software was superior to what Amazon had deployed in some respects.
It said the website glitches experienced on Prime Day came at a time when the company was also trying to hose down an issue at one of its bigger warehouses in Ohio. Together, these led to thousands of deliveries being delayed.
The report obtained by CNBC, running to 25 pages, showed that Amazon's technical staff struggled to find out the root cause of the issues on Prime Day.
The worker entered one wrong input for the command and ended up removing a much larger number of servers than intended, some of which supported two other S3 subsystems.
CNBC said Amazon also failed to come up with a contingency plan in the event of any error in its replacement database, which is the open-source PostgreSQL software, sold by a company known as Aurora.
One of the questions in the Amazon technical report obtained by CNBC asked the engineers why the database system had not failed during the previous Prime Day when it was running on Oracle. They said that Oracle and Aurora PostgreSQL handled savepoints differently.
An Amazon spokesperson attempted to play down the issue and even claimed there was no outage, even though the report that CNBC obtained said that the "degradation resulted in lags and complete outages".
CNBC said 13 warehouses had moved from Oracle to PostgreSQL before Prime Day. It said the Amazon report cited delayed deliveries for 15,000 packages and about US$90,000 in wasted labour costs.