Immutable & mutable infrastructure

Example:

You add a database to your infrastructure: VM, VPC + database. Scale it 1000 times.

Mutable approach - environment (configuration) drift (move the infrastructure from V1 to V2 with a mutation custom script):

• 99% it is working, but 1% failing in a limbo state.
• Existing environment no longer matches what we have in our automation.
• To debug you would have to:
  • wipe out the entire environment
  • redeploy V1
  • run those scripts
• When moving to scale it becomes incredibly hard to maintain.

Immutable approach - a new environment alongside the old one:

• When they are both working you bring down the older version.
• It is expensive (V1 and V2 are running at the same time).
• But it's a best practice to ensure that your infrastructure can scale.