Partition key selection in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a partition key in DynamoDB?

A partition key is the primary attribute used to distribute data across partitions in DynamoDB. It determines where the data is stored and how it is accessed.

beginner

Why is choosing a good partition key important?

A good partition key ensures even data distribution and avoids 'hot partitions' that can slow down performance. It helps DynamoDB scale efficiently.

intermediate

What happens if a partition key has low cardinality?

Low cardinality means few unique values for the partition key. This causes uneven data distribution and can create hot partitions, leading to slower queries.

intermediate

How can you choose a partition key to avoid hot partitions?

Pick a key with many unique values that are accessed evenly. For example, use user IDs or order IDs instead of a fixed status or category.

beginner

What is a composite primary key in DynamoDB?

A composite primary key uses both a partition key and a sort key. This allows multiple items to share the same partition key but be uniquely identified by the sort key.

What does the partition key in DynamoDB determine?

A The number of tables

B The size of the database

C Where data is stored and how it is accessed

D The encryption method

The partition key determines the physical location of data and how DynamoDB accesses it.

Which is a sign of a poor partition key choice?

A Many unique values

B Low cardinality causing hot partitions

C Even data distribution

D Using user IDs

Low cardinality means few unique values, causing uneven data distribution and hot partitions.

What is a composite primary key made of?

A Partition key and sort key

B Two partition keys

C Sort key only

D Partition key and timestamp

A composite primary key combines a partition key and a sort key to uniquely identify items.

Which attribute is best for a partition key?

A User ID with many unique values

B Fixed category name

C Status with values like 'open' or 'closed'

D Boolean flag

User ID usually has many unique values, helping distribute data evenly.

What problem do hot partitions cause?

A Automatic backups

B Faster queries

C More storage space

D Slower performance and throttling

Hot partitions cause slower performance because too many requests target the same partition.

Explain why selecting a good partition key is important in DynamoDB.

Think about how data is stored and accessed.

Describe what a composite primary key is and when you might use it.

Consider how to store related items together.