Filter expressions in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a filter expression in DynamoDB?

A filter expression is a condition that DynamoDB applies after retrieving items to decide which items to return to you. It filters out items that don't match the condition.

intermediate

When is a filter expression applied during a DynamoDB query or scan?

Filter expressions are applied after DynamoDB reads the items. They do not reduce the read capacity units consumed but only reduce the data returned to you.

beginner

Which operators can you use in a DynamoDB filter expression?

You can use comparison operators like =, <, >, <=, >=, <> and logical operators like AND, OR, NOT in filter expressions.

beginner

True or False: Filter expressions reduce the number of read capacity units consumed by DynamoDB.

False. Filter expressions do not reduce read capacity units because filtering happens after reading the data.

beginner

How do you write a filter expression to find items where the attribute 'status' equals 'active'?

You write: "#status = :val" and provide a value map with ":val" set to "active" and an expression attribute names map with "#status" set to "status".

When does DynamoDB apply a filter expression?

A During table creation

B Before reading items from the table

C After reading items, before returning results

D When updating items

Filter expressions are applied after DynamoDB reads the items to decide which items to return.

Which of these is a valid operator in a DynamoDB filter expression?

A =

B ++

C &&&

D ===

The '=' operator is valid for comparison in filter expressions.

Does using a filter expression reduce the read capacity units consumed?

A Yes, always

B No, never

C Only for queries, not scans

D Only if the filter expression is simple

Filter expressions do not reduce read capacity units because filtering happens after data is read.

Which DynamoDB operation can use filter expressions?

A Both Query and Scan

B Query

C Scan

D PutItem

Both Query and Scan operations support filter expressions.

What is the purpose of a filter expression?

A To filter items before reading them

B To update items conditionally

C To create indexes

D To filter items after reading them

Filter expressions filter items after DynamoDB reads them, controlling what is returned.

Explain what a filter expression is and when it is applied in DynamoDB operations.

Think about when DynamoDB reads data and when it decides what to return.

Describe how to write a simple filter expression to return items where an attribute equals a specific value.

Remember the syntax uses placeholders for values.