Item size limits and considerations in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Maximum item size in DynamoDB

What is the maximum size allowed for a single item in DynamoDB, including all attribute names and values?

A 256 KB

B 1 MB

C 400 KB

D 100 KB

💡 Hint

Think about the official documented limit for item size in DynamoDB.

DynamoDB limits the total size of an item, including attribute names and values, to 400 KB.

🧠 Conceptual

intermediate

Impact of large items on DynamoDB performance

Which of the following is a true statement about storing very large items close to the 400 KB limit in DynamoDB?

A Large items have no impact on performance or cost.

B Large items reduce the cost because fewer items are stored.

C Large items automatically compress to save space and speed up queries.

D Large items increase read and write latency and consume more throughput capacity.

💡 Hint

Think about how size affects throughput and latency in databases.

Large items consume more read/write capacity units and can increase latency because more data is transferred and processed.

📝 Syntax

advanced

Identify the error in this DynamoDB item size calculation

Given this JSON item stored in DynamoDB, which option correctly calculates the total item size?

{"UserId": "12345", "Profile": {"Name": "Alice", "Bio": "A short bio."}}

A Count only the number of attributes ignoring their values

B Sum of UTF-8 bytes of all attribute names and values including nested attributes

C Sum of characters in attribute values only

D Sum of attribute names only

💡 Hint

Remember that DynamoDB counts bytes, not characters, and includes attribute names and nested attributes.

DynamoDB calculates item size by summing the UTF-8 encoded bytes of all attribute names and values, including nested attributes.

❓ optimization

advanced

Best practice to handle items exceeding size limits

You have items that exceed the 400 KB limit in DynamoDB. Which approach is best to handle this situation?

A Split the large item into multiple smaller items and use a composite key to link them.

B Store the entire large item as a single attribute using a string type.

C Increase the item size limit in DynamoDB settings.

D Compress the item data and store it as binary without splitting.

💡 Hint

DynamoDB does not allow increasing item size limits. Think about splitting data logically.

Since DynamoDB has a fixed 400 KB item size limit, splitting large items into smaller linked items is the recommended approach.

🔧 Debug

expert

Why does this DynamoDB PutItem operation fail?

A developer tries to insert this item but gets a ValidationException error:

{"OrderId": "001", "Details": {"Description": "A very long text exceeding 400 KB..."}}

What is the most likely cause?

A The total item size exceeds the 400 KB limit allowed by DynamoDB.

B The attribute name 'Details' is reserved and cannot be used.

C The 'OrderId' attribute must be a number, not a string.

D DynamoDB does not support nested JSON objects in items.

💡 Hint

Consider DynamoDB limits on item size and attribute types.

DynamoDB enforces a 400 KB limit on item size. Large nested attributes can cause the item to exceed this limit, resulting in a ValidationException.