Mistake 1: One account to rule the all
Ideally, at least 3 accounts is needed:
Mistake 2: Writing your own management tool
There are a lot of good tools out there
Mistake 3: Jumping into any freshly announced service
At least wait until Cloudformation/Terraform supports it
Mistake 4: Using any platform DB before figuring out how to backup
DynamoDB backup is still not easy, there is no out-of-the-box backup solution
Mistake 5: Believing in Multi-AZ
The truth is: it has a higher chance to lose an important service in a whole region (S3, Dynamo, Kinesis), than losing an AZ.
If you want better SLA than AWS, go multi-region from the beginning.
Mistake 6: Using IAM users instead of roles for services
It can be hard to change it later
By Tusa Viktor