GSI key selection strategy in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Global Secondary Index (GSI) in DynamoDB?

A GSI is an index with a partition key and optional sort key that can be different from the base table's keys. It allows querying data efficiently using alternate keys.

beginner

Why is key selection important when creating a GSI?

Choosing the right keys ensures efficient queries, balanced data distribution, and avoids hot partitions that can slow down performance.

intermediate

What should you consider about data distribution when selecting a GSI partition key?

Pick a key with many distinct values that spread requests evenly across partitions to prevent bottlenecks.

intermediate

How does the choice of a GSI sort key affect query flexibility?

A sort key lets you filter and sort data within a partition, enabling more precise and efficient queries.

advanced

What is a common mistake when selecting GSI keys?

Choosing keys with low cardinality or skewed data can cause hot partitions and reduce query performance.

What is the main purpose of a GSI in DynamoDB?

A To store backup copies of data

B To increase write throughput only

C To allow queries on attributes other than the primary key

D To encrypt data automatically

A GSI lets you query data efficiently using alternate keys different from the table's primary key.

Which characteristic is best for a GSI partition key?

A Few distinct values with uneven access

B Many distinct values with even access

C A constant value for all items

D A large text attribute

Many distinct values with even access help distribute load evenly and avoid hot partitions.

How does a GSI sort key improve queries?

A It allows filtering and sorting within a partition

B It encrypts the data

C It increases storage capacity

D It speeds up writes

A sort key lets you filter and sort data within the same partition key, making queries more flexible.

What happens if a GSI partition key has low cardinality?

A Hot partitions may form, causing slow queries

B Data is evenly distributed

C The index automatically scales

D Queries become faster

Low cardinality means few distinct values, which can cause uneven load and slow down queries.

Which is NOT a good practice when selecting GSI keys?

A Choosing keys with many distinct values

B Selecting keys that match query patterns

C Including a sort key for filtering

D Using keys with skewed data distribution

Keys with skewed data cause hot partitions and reduce performance, so they should be avoided.

Explain how to choose a good partition key for a GSI in DynamoDB.

Think about how to spread workload evenly and support your queries.

Describe the role of a sort key in a GSI and how it affects querying.

Consider how you can narrow down results inside one partition.