DynamoDB CRUD, Query, Scan, GSI and TTL Step by Step

By Ravindra Bagale, trainer · LinkedIn · Last updated: 23 October 2026

1. A story: find orders by email without scanning the world

Orders table PK is orderId. Support asks: show all orders for rita@mail.test. A Scan of every order works for 50 rows and dies at 5 million. The fix is a Global Secondary Index with PK email and SK createdAt, then a Query.

2. CRUD basics

What is it?

• PutItem — create or replace a whole item.
• GetItem — read by full primary key (PK + SK if you have one).
• UpdateItem — change some attributes.
• DeleteItem — remove by key.
• Query — all items under one PK (optional SK condition). Uses indexes efficiently.
• Scan — walk the table or index; filter after read. Costs for every item examined.

Why Scan costs more: billing for reads is based on data examined, not only data returned. A filter that throws away 99% still charged you for reading it.

3. GSI vs LSI

4. TTL, Streams and backups

• TTL: an attribute holding a Unix epoch second. When time passes, DynamoDB deletes the item for free in the background. Great for sessions and temp links.
• Streams: a time-ordered log of item changes. Lambda can process inserts/updates/deletes (sync search index, drive workflows).
• Backups: on-demand backup or point-in-time recovery (PITR) for restore. Turn PITR on for important tables.

5. Code: Put and Query

Python (boto3)

import boto3
from boto3.dynamodb.conditions import Key
table = boto3.resource("dynamodb", region_name="ap-south-1").Table("OrdersLab")
table.put_item(Item={"orderId": "O1", "email": "rita@mail.test", "total": 499})
# After GSI EmailIndex (PK email, SK orderId):
r = table.query(IndexName="EmailIndex", KeyConditionExpression=Key("email").eq("rita@mail.test"))
print(r["Items"])

Node.js (@aws-sdk/client-dynamodb)

import { DynamoDBClient, PutItemCommand, QueryCommand } from "@aws-sdk/client-dynamodb";
const c = new DynamoDBClient({ region: "ap-south-1" });
await c.send(new PutItemCommand({ TableName: "OrdersLab",
  Item: { orderId: { S: "O1" }, email: { S: "rita@mail.test" }, total: { N: "499" } } }));
const q = await c.send(new QueryCommand({ TableName: "OrdersLab", IndexName: "EmailIndex",
  KeyConditionExpression: "email = :e", ExpressionAttributeValues: { ":e": { S: "rita@mail.test" } } }));
console.log(q.Items);

Java (AWS SDK v2)

DynamoDbClient ddb = DynamoDbClient.builder().region(Region.AP_SOUTH_1).build();
ddb.putItem(PutItemRequest.builder().tableName("OrdersLab")
  .item(Map.of("orderId", AttributeValue.fromS("O1"),
               "email", AttributeValue.fromS("rita@mail.test"),
               "total", AttributeValue.fromN("499"))).build());

PHP (AWS SDK for PHP)

$ddb = new Aws\DynamoDb\DynamoDbClient(['region'=>'ap-south-1','version'=>'latest']);
$ddb->putItem(['TableName'=>'OrdersLab','Item'=>[
  'orderId'=>['S'=>'O1'], 'email'=>['S'=>'rita@mail.test'], 'total'=>['N'=>'499']
]]);

6. Lab: Query, GSI and TTL

How to do it (step by step)

1. Create table OrdersLab, PK orderId (S), on-demand.
2. Put three items with different orderId and emails (console or CLI).
3. Indexes → Create index → GSI name EmailIndex, PK email (S), SK orderId (S), on-demand → Create. Wait until Active.
4. Query on EmailIndex with one email — only that user's orders. Compare a Scan with a filter on email — works, but note Consumed capacity is higher on large tables.
5. Additional settings → TTL → enable attribute expiresAt. Put an item with expiresAt = now+120 (epoch seconds). After a few minutes it disappears (TTL is eventually processed, not instant).
6. Backups → Edit PITR → On (optional for lab).

Cleanup

1. Delete table OrdersLab (deletes GSIs). Turn off PITR first if prompted.

7. Interview questions

Revision, comparison and interview cards

Revise this lesson in a few minutes. Save the cards on your phone or download them as PNG files. The QR code on each card opens this lesson.

More cards: Ravi Sir's Cards.