15 Things To know About Amazon Web Service’s Dynamo DB service. This helped me pass (crush) the developer associate Certification.
Get a quick overview of DynamoDB. These points are super helpful if you’re taking the AWS certificate, especially the Developer associate.
1) Dynamo DB where DB stands for database, is a NOSQL managed database service provided by AWS. Data is stored in JSON like format.
2) It scales up and down seamlessly through API calls or CLI calls.
3) Even though DynamoDB is a cloud service you can download the software for your local machine.
4) Provisioned Throughput When you create a table or index in Amazon DynamoDB, you must specify your capacity requirements for read and write activity. This unit of capacity is called Provisioned Throughput.
5) There are 2 types of reads in DynamoDB: Strongly consistent read and eventually consistent read. Eventual consistent read is by default and takes half the throughput unit. Example: 4 eventually consistent reads = 2 strongly consistent read.
6) 1 read unit is up to 4KB each. So If you need to write 16 KB of item every second, you will need 16/4 which is 4 strong read capacity. Further, if it’s eventual consistency, divide by 2 to get 2 read units.
7) Each write unit is 1KB each so if you have 5 items with 5 KB each, the number of write capacity is 5*5 which is 25.
8) DynamoDB writes operations(PutItem, UpdateItem, DeleteItem)are by default Unconditional, meaning they will overwrite items with same partition key. But there is a conditional-write options for writes where item is written only after fulfilling certain conditions.
9) You can use BatchGetItem or BatchWriteItem when you need to read or write multiple items to or from table at a time.
10)The number of tables per account is limited to 256 initially and can be increased by contacting support. On the other hand, the size of the table is unconstrained in terms of number of items.
11)The Number of Read and Write Capacity Units have a limit by default by different Regions but can be increased by contacting AWS support.
12)You can have a total of 10 secondary index where maximum of 5 Local secondary Index and where maximum of 5 Global secondary Index can be there. These limits cannot be increased.
13)Local Secondary index HAS to be created at the time of table creation. Global secondary index can be created at any time. Local Secondary index must have the same partition key as the item partition key. Global’s doesn’t need to.
14)Query and Scan are 2 ways to retrieve items from a table. Query is more efficient.
15)If certain items in a table are very popular and accessed more frequently compared to others you can Cache the popular items. Caching popular items will reduce your read capacity and save you money.