The DynamoDB Free Tier: What You Actually Get

Every article about DynamoDB's free tier gives you the raw numbers without context. 25 WCU, 25 RCU, 25GB. But what does that actually mean in terms of real application usage? Here is the practical breakdown.

The Raw Numbers

AWS DynamoDB free tier (perpetual, does not expire):

• 25 Write Capacity Units (WCU): Up to 25 writes/second (items up to 1KB)
• 25 Read Capacity Units (RCU): Up to 25 reads/second (strongly consistent, items up to 4KB)
• 25 GB storage: Data plus indexes
• 2 Global Secondary Indexes per table

What That Translates To

Writes (25 WCU)

25 writes per second = 2.16 million writes per day = 64.8 million writes per month.

For a blog platform, writes happen when:

• Creating a new post (1 write)
• Updating a post (1 write)
• Adding a subscriber (1 write)
• Recording a newsletter send (1 write)

At 64.8 million writes per month, you could create 2 million blog posts per month and still be within the free tier. No blog needs that.

Reads (25 RCU)

25 strongly consistent reads per second for items up to 4KB. For eventually consistent reads (which is fine for a blog), you get 50 reads per second.

50 reads/second = 4.32 million reads per day = 129.6 million reads per month.

For a blog:

• Each page view requires 1-2 reads (post data + categories)
• At 50 reads/second, you handle 25 concurrent page views
• With frontend caching (revalidate:60), most requests never hit DynamoDB

Storage (25 GB)

A typical blog post (title, body, metadata) is 5-10KB. At 10KB per post:

• 25 GB = ~2.5 million posts
• Plus GSI storage (roughly doubles the data)
• So approximately 1.25 million posts within free tier

The Gotcha: Provisioned vs On-Demand

The free tier ONLY applies to provisioned capacity mode. On-demand mode is pay-per-request and does not qualify for the free tier.

# Correct: provisioned mode (free tier eligible)
table = dynamodb.create_table(
    TableName='plai-content',
    ProvisionedThroughput={
        'ReadCapacityUnits': 5,
        'WriteCapacityUnits': 5,
    },
    # ...
)
 
# Wrong: on-demand mode (charges per request, no free tier)
table = dynamodb.create_table(
    TableName='plai-content',
    BillingMode='PAY_PER_REQUEST',
    # ...
)

The GSI Limit

You get 2 GSIs per table within the free tier. Each GSI has its own provisioned capacity that counts against the 25 WCU/RCU limits. Plan your access patterns carefully. Two GSIs are enough for most simple applications.

The Bottom Line

For a blog, portfolio, or small SaaS with moderate traffic, DynamoDB's free tier is more than sufficient. The key is using provisioned mode, keeping items small, and leveraging frontend caching to reduce database reads.

See the DynamoDB pricing page for the current free tier details.