Amazon DynamoDB vs Riak

• DynamoDB is fully-managed. In the early days, it lacked features like backups, and developers had to either implement some of their own backup functionality or live dangerously. Today, DynamoDB's claim to be fully-managed is more credible. Backups can be configured through the console. Table capacity does not even need to be planned anymore; you can scale (and pay) on-demand.
• DynamoDB is inexpensive for some use-cases. In particular, DynamoDB is very inexpensive when you create a datastore for a low-volume micro-service, or a stateful background job. DynamoDB is much less expensive than RDS or Elasticache for these use-cases, and it allows developers to design systems without worrying about cost.
• DynamoDB is fast when used for the use-cases it was designed for.
• DynamoDB supports the development experience and testing reasonably well. AWS provides an official DynamoDB image that can be used in tests locally or in CI.

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• Highly available: If nodes go offline for any reason, the system still operates.
• Highly scalable: There is a minimum of 5 nodes, which can handle a lot by themselves. When scaling is required, it can be done easily, with minimal to no downtime on large scales.
• Very fast searching: Riak has SOLR indexing built-into the core product, which makes querying for data very fast.

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• Capacity planning can be difficult, but it is probably a worthwhile exercise in itself. However, today you can scale tables on-demand without capacity planning.
• Migrations can be slow and difficult. If you need to change your schema (e.g., add a secondary index) after you have written a large volume of data to the table or after consumers of the data are live, migrating can be expensive. Tooling for DynamoDB migrations is less mature than tools for migrating other datastores.
• The API is complicated, and third-party wrappers, like PynamoDB, are immature.
• Scanning tables is slow and expensive. It is important to anticipate all of the types of queries you will need to support and design your schema accordingly.

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• At the time I was using Riak, data was stored as blobs so you couldn't query the data directly on the server. This has since been remedied with the addition of full-text search support.

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• Dynamodb reduced the need for SRE headcount to maintain infrastructure.
• Built in metrics dove tails with existing monitoring tooling.
• Flexible NoSQL design allows developers to focus on business problems, rather than database design.

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• It provided a solution for use to securely write data to the cloud. This has been instrumental in allowing us to move more applications to the cloud. Writes are performed behind firewalls and then replicated to the cloud for application consumption. By moving more applications to the cloud, we free up internal resources and can serve information in a much more scalable and reliable way.

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