• ​Best Practices​

• ​https://aws.amazon.com/dynamodb/getting-started/​

• ​https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-general-nosql-design.html​

Node.js

To store Timestamp:

new Date().toISOString()

Designing Your Tables

• Unlike traditional RDBMs, DynamoDB groups sorts by partitions.

  • Each partition returns sorted result.

Gotchas

Serverless

WARNING: Changing the table name in serverless.yml will drop the table.

DynamoDB Shell

• ​http://localhost:8000/shell​

• Works better in Chrome vs Safari

​Reserved Words​

• counter

• name

• source

• url

• uuid

• value

Promises (async/await)

const { promisify } = require('util');
...
dynamodb.putPromise = promisify(dynamodb.put);
dynamodb.updatePromise = promisify(dynamodb.update);
dynamodb.getPromise = promisify(dynamodb.get);
...
result = await dynamodb.putPromise({});
result = await dynamodb.updatePromise({});
result = await dynamodb.getPromise({});
​

​GetItem​

// Does not throw an exception if record does not exist
const result = await dynamodb.getPromise({});
​
if (!result.Item) {
  // exit early
}

GetItem cannot be preformed on a Global Secondary Index.

​PutItem​

Will overwrite values if the key is the same; unless you define a ConditionalExpression

If an item that has the same primary key as the new item already exists in the specified table, the new item completely replaces the existing item. You can perform a conditional put operation (add a new item if one with the specified primary key doesn't exist), or replace an existing item if it has certain attribute values. You can return the item's attribute values in the same operation, using the ReturnValuesparameter.

​ConditionalExpression​

docClient.put(
  {
    TableName: 'Example',
    Item: {
      CounterName: 'Example1',
    },
    ConditionExpression: 'attribute_not_exists(CounterName)'
  },
  function (error, data) {
    if (error) {
      // If conflict, an error will be thrown
    } else {
      
    }
  }
);

When using ConditionExpression, and if there is a conflicting.

Sample error:

{
    "message":"The conditional request failed",
    "code":"ConditionalCheckFailedException",
    "time":"2019-02-03T09:20:20.260Z",
    "statusCode":400,
    "retryable":false
}

Query vs Scan

​https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Query.html https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Scan.html​

Indexes

Sorting is all done on the same partition.

Have to partition wisely.

​https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-indexes-general.html​https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/SecondaryIndexes.html​

Global Secondary Index

Cannot perform GetItem. Use Query or Scan. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-indexes-general.html​