AWS DynamoDB: Put Item into a Table

Putting Items into DynamoDB

The aws dynamodb put-item command creates a new item or replaces an existing item in a DynamoDB table. Items are specified in DynamoDB's JSON format, which includes type descriptors.

Basic Put Item

aws dynamodb put-item \
  --table-name Users \
  --item '{
    "userId": {"S": "user-001"},
    "name": {"S": "Alice Johnson"},
    "email": {"S": "alice@example.com"},
    "age": {"N": "28"},
    "active": {"BOOL": true},
    "tags": {"L": [{"S": "admin"}, {"S": "developer"}]}
  }'

DynamoDB JSON Type Descriptors

Type	Key	Example
String	S	{"S": "hello"}
Number	N	{"N": "42"} (always a string)
Boolean	BOOL	{"BOOL": true}
Null	NULL	{"NULL": true}
List	L	{"L": [{"S": "a"}, {"N": "1"}]}
Map	M	{"M": {"key": {"S": "val"}}}
String Set	SS	{"SS": ["a", "b"]}
Number Set	NS	{"NS": ["1", "2"]}

Conditional Put (prevent overwriting)

aws dynamodb put-item \
  --table-name Users \
  --item '{"userId": {"S": "user-001"}, "name": {"S": "Alice"}}' \
  --condition-expression "attribute_not_exists(userId)"

This fails with ConditionalCheckFailedException if the item already exists.

Return Old Values

aws dynamodb put-item \
  --table-name Users \
  --item '{"userId": {"S": "user-001"}, "name": {"S": "Alice Updated"}}' \
  --return-values ALL_OLD

Returns the previous version of the item before it was replaced.

From File

aws dynamodb put-item \
  --table-name Users \
  --item file://item.json