TTL with Streams for archival in DynamoDB - Step-by-Step Execution

Concept Flow - TTL with Streams for archival

Item inserted in DynamoDB table

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TTL attribute set with expiry timestamp

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Time passes until TTL expires

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DynamoDB deletes expired item

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Stream captures deletion event

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Lambda triggered by Stream event

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Lambda archives deleted item to S3 or another store

This flow shows how DynamoDB TTL deletes expired items, streams capture the deletion, and a Lambda archives the deleted data.

Execution Sample

DynamoDB

1. Insert item with TTL attribute (expiry timestamp)
2. Wait until TTL expires
3. DynamoDB deletes item
4. Stream records deletion event
5. Lambda triggered by stream
6. Lambda archives item

This sequence shows how an item with TTL is deleted and archived via DynamoDB Streams and Lambda.

Execution Table

Step	Action	TTL Attribute	Stream Event	Lambda Triggered	Archive Action
1	Insert item	TTL set to future timestamp	No	No	No
2	Wait for TTL expiry	TTL timestamp reached	No	No	No
3	DynamoDB deletes expired item	Expired	Deletion event generated	No	No
4	Stream sends deletion event	Expired	Deletion event present	No	No
5	Lambda triggered by stream	Expired	Deletion event present	Yes	Started archiving
6	Lambda archives item	Expired	Deletion event present	Yes	Item archived
7	Process complete	Expired	Deletion event processed	No	Archive done

💡 Process stops after Lambda archives the deleted item from the stream event.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	Final
Item TTL	None	Future timestamp set	Expired	Expired	Expired
Stream Event	None	None	Deletion event generated	Deletion event present	Processed
Lambda Triggered	No	No	No	Yes	No
Archive Status	Not started	Not started	Not started	Started	Done

Key Moments - 3 Insights

Why doesn't the Lambda trigger immediately after setting the TTL attribute?

Because TTL expiry happens asynchronously after the timestamp passes, so the stream deletion event only appears after DynamoDB deletes the expired item (see execution_table step 3 and 4).

What does the stream capture when an item expires?

The stream captures a deletion event for the expired item, which triggers the Lambda to archive it (see execution_table step 4).

Can the Lambda archive the item before the TTL expiry?

No, the Lambda only triggers after the deletion event from the stream, which happens after TTL expiry and item deletion (see execution_table steps 3 to 5).

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the Lambda first get triggered?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Check the 'Lambda Triggered' column in execution_table rows.

According to variable_tracker, what is the Archive Status after Step 5?

A Not started

B Started

C Done

D Failed

💡 Hint

Look at the 'Archive Status' row and the 'After Step 5' column.

If the TTL attribute is never set, what happens to the stream event?

A No deletion event is generated

B Lambda triggers without event

C Deletion event is generated anyway

D Item is archived immediately

💡 Hint

Refer to the flow where TTL expiry causes deletion and stream event.

Concept Snapshot

DynamoDB TTL deletes expired items automatically.
Deletion triggers a stream event.
Lambda listens to stream events.
Lambda archives deleted items.
This automates archival after TTL expiry.

Full Transcript

This visual execution shows how DynamoDB TTL works with Streams for archival. First, an item is inserted with a TTL attribute set to a future timestamp. Time passes until the TTL expires. DynamoDB then deletes the expired item. This deletion generates a stream event. The stream event triggers a Lambda function. The Lambda archives the deleted item to an external store like S3. Variables like TTL attribute, stream event presence, Lambda trigger, and archive status change step-by-step. Key moments clarify that Lambda triggers only after deletion, and the stream captures deletion events only after TTL expiry. The quiz tests understanding of when Lambda triggers, archive status progression, and what happens if TTL is not set.