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Code Issues Releases Wiki Activity

Dynamodb improvements (#558)

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Corey Quinn 2017-12-04 22:10:18 -07:00 committed by Thanos Baskous
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@ -1307,6 +1307,7 @@ DynamoDB
- DynamoDB can be used [as a simple locking service](https://gist.github.com/ryandotsmith/c95fd21fab91b0823328).
- DynamoDB indexing can include **primary keys**, which can either be a single-attribute hash key or a composite hash-key range. You can also query non-primary key attributes using [**secondary indexes**](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/SecondaryIndexes.html).
- **Data Types:** DynamoDB supports three [data types](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DynamoDBMapper.DataTypes.html) – **number**, **string**, and **binary** – in both scalar and multi-valued sets. DynamoDB can also support [**JSON**](https://aws.amazon.com/blogs/aws/dynamodb-update-json-and-more/).
- As of late 2017, DynamoDB supports both [global tables](https://aws.amazon.com/dynamodb/global-tables/) and [backup / restore functionality](https://aws.amazon.com/dynamodb/backup-restore/).
### DynamoDB Gotchas and Limitations
@ -1314,7 +1315,6 @@ DynamoDB
- 🔸 It is important to make sure that DynamoDB [resource limits](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html#limits-data-types) are compatible with your dataset and workload. For example, the maximum size value that can be added to a DynamoDB table is 400 KB (larger items can be stored in S3 and a URL stored in DynamoDB).
- 🔸 Dealing with **time series data** in DynamoDB can be challenging. A global secondary index together with down sampling timestamps can be a possible solution as explained [here](https://blogs.aws.amazon.com/bigdata/post/Tx3KPZDXIBJEQ4B/Scaling-Writes-on-Amazon-DynamoDB-Tables-with-Global-Secondary-Indexes).
- 🔸 DynamoDB does [not allow](https://forums.aws.amazon.com/thread.jspa?threadID=90137) an empty string as a valid attribute value. The most common work-around is to use a substitute value instead of leaving the field empty.
- 🔸 DynamoDB does not support moment-in-time/snapshot backups. It is not possible to create a moment-in-time view of a table without preventing all writes to a table and then consistently reading it. You can't work around this using [Cross-Region Replication](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.CrossRegionRepl.html) because under the covers, it uses [DynamoDB Streams](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Streams.html). In a Stream, the order in which Items appear can be different than the order in wihch they were written. Only updates to the same Item are guaranteed to be ordered.
- 🔸 When setting up [fine grained policies](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/specifying-conditions.html) for access to DynamoDB tables, be sure to include their secondary indices in the policy document as well.