maximum number of database (Dynamo DB) in a single AWS account.

In Amazon DynamoDB, there isn't a concept of separate databases within a single AWS account. Instead, DynamoDB uses tables as the primary organizational unit for data.

For your scenario with 20 distributors (and potentially more in the future), you can create separate tables for each distributor within a single AWS account. This approach allows you to maintain isolation between distributors' data while still managing everything within one account.

Regarding the maximum number of tables in DynamoDB:

1. You can create up to 2500 tables per AWS Region in a single account. This limit should be more than sufficient for your current needs of 20 distributors and allows for significant future growth.

2. There's no limit on the number of items (rows) or the size of a single table, so you can store vast amounts of data for each distributor.

If you need more than 2500 tables in the future, you can request a service quota increase through AWS Support.

For your ERP system, you could structure your data as follows:

• Create separate tables for each distributor's inventory (e.g., "Distributor1_Inventory", "Distributor2_Inventory", etc.)
• Create separate tables for each distributor's financial accounting (e.g., "Distributor1_Financials", "Distributor2_Financials", etc.)

This approach allows you to easily manage and scale your system as the number of distributors increases. If you ever reach the table limit and can't get it increased, you could consider using a multi-tenant model where data from multiple distributors is stored in the same table, using a partition key to distinguish between distributors. However, with the current limit of 2500 tables, you have ample room for growth before needing to consider such an approach.

Remember, DynamoDB is designed to scale elastically, so you don't need to worry about the size of individual tables as your data grows. Focus on designing your table structure to support your application's access patterns efficiently.
Sources
FAQ - AWS Prescriptive Guidance
Overview of Amazon DynamoDB - Best Practices for Migrating from RDBMS to Amazon DynamoDB