Reading and Writing Data

DynamoDB provides a rich set of API operations for reading and writing data. This lesson covers the core operations — PutItem, GetItem, UpdateItem, DeleteItem, Query, and Scan — along with conditional expressions, batch operations, and transactions.

---

Write Operations

PutItem

Creates a new item or replaces an existing item with the same primary key:

aws dynamodb put-item \
  --table-name Users \
  --item '{
    "UserId": {"S": "user-001"},
    "Name": {"S": "Alice"},
    "Email": {"S": "alice@example.com"},
    "Age": {"N": "30"}
  }'

Important: PutItem replaces the entire item. If an item with the same key exists, all attributes are overwritten.

UpdateItem

Modifies specific attributes of an existing item (or creates it if it does not exist):

aws dynamodb update-item \
  --table-name Users \
  --key '{"UserId": {"S": "user-001"}}' \
  --update-expression "SET Age = :newAge, UpdatedAt = :ts" \
  --expression-attribute-values '{
    ":newAge": {"N": "31"},
    ":ts": {"S": "2024-03-04T12:00:00Z"}
  }'

Update Expression Actions