Introduction to Amazon DynamoDB

Amazon DynamoDB is a fully managed, serverless, key-value and document database designed to deliver single-digit-millisecond performance at any scale. It handles more than 10 trillion requests per day and can support peaks of more than 20 million requests per second. DynamoDB is the backbone of many high-profile AWS services and customers including Amazon.com, Lyft, Airbnb, and Capital One.

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Why DynamoDB?

Traditional relational databases scale vertically — you buy a bigger server when you need more capacity. DynamoDB scales horizontally by partitioning data across many servers automatically. This architecture delivers:

• Consistent single-digit-millisecond latency regardless of table size
• Virtually unlimited throughput and storage — no need to provision or manage servers
• Built-in high availability — data is replicated across three Availability Zones
• Serverless operations — no patching, no backups to schedule, no capacity planning

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Core Concepts

Tables

A DynamoDB table is a collection of items. Unlike a relational table, items in the same DynamoDB table can have different attributes (schema-less within the table).

Items

An item is a single data record, similar to a row in a relational table. Each item is uniquely identified by its primary key and can be up to 400 KB in size.

Attributes

Attributes are the data elements within an item, analogous to columns. DynamoDB supports scalar types (String, Number, Binary, Boolean, Null), document types (List, Map), and set types (String Set, Number Set, Binary Set).

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Primary Keys

Every DynamoDB table requires a primary key. There are two types:

Partition Key (Simple Primary Key)

A single attribute that DynamoDB uses to hash and distribute items across partitions.

Table: Users
Partition Key: userId

┌──────────┬──────────────┬───────────┐
│ userId   │ name         │ email     │
├──────────┼──────────────┼───────────┤
│ U001     │ Alice Smith  │ a@ex.com  │
│ U002     │ Bob Jones    │ b@ex.com  │
└──────────┴──────────────┴───────────┘

Composite Primary Key (Partition Key + Sort Key)

Two attributes: the partition key determines which partition stores the item, and the sort key orders items within that partition. This enables efficient range queries.

Table: Orders
Partition Key: customerId
Sort Key: orderDate

┌────────────┬────────────┬─────────┬────────┐
│ customerId │ orderDate  │ orderId │ total  │
├────────────┼────────────┼─────────┼────────┤
│ C001       │ 2025-01-15 │ ORD-101 │ 49.99  │
│ C001       │ 2025-03-22 │ ORD-205 │ 129.00 │
│ C002       │ 2025-02-10 │ ORD-150 │ 74.50  │
└────────────┴────────────┴─────────┴────────┘

With this design you can efficiently query all orders for customer C001 between two dates.

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Data Types