If you're working with DynamoDB, you're likely to rely on Condition Expressions when manipulating items in your table. Condition Expressions can ensure you don't overwrite existing users, allow bank account balances to drop below \$0, or give Admin access to every user in your application.
Yet despite their usefulness, I see Condition Expressions misunderstood quite often. My hunch is that this is due to an underdeveloped mental model of how DynamoDB works and why it makes the choices it makes.
In this post, you'll learn all about DynamoDB's Condition Expressions. First, we'll start with some background on what Condition Expressions are. We'll see why they are helpful and the API operations to which they apply.