As of majority cases, documentation is poor or missing.

• In order to get it working, EC2 should be tagged with backupEnabled tag which has value yes || Yes || YES

• retention tag should have integer value how long backups are preserved

• Create IAM policy and attach policy to Role. Policy must have next values:

• DescribeInstances

• CreateSnapshot

• CreateSnapshots

• CreateTags

• DescribeSnapshots

• DeleteSnapshot

• pick Author from scratch on right upper side
• give it a name
• and choose previously created role
• select Python 2.7 interpreter and paste ebsSnapshot.py content. Please, copy it from RAW page to be sure you will not have issues with execution.
• increase timeout to 3 mins
• add environment variables
• name: region
• value: eg. us-east-1
• only for ebsCleanup function add account_id environment variable with account id of your account
• click on Triggers
• add new trigger clicking on CloudWatch Events
• select schedule and set up cron expression, eg. 0 12 * * ? *

Repeat the process for deleting snapshots with DeleteOn flag.

Additionally, you can set SNS to send notification whenever Lambda reported an error. With CloudWatch you can create dashboard with Invocations, Duration, Throttles and Errors.