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DynamoDB Queries

  • Allow you to find items using only primary key values from table or secondary index
  • Benefits:
    • Returns the item matching the primary key search
    • Much more efficiency because it searches indexes only
    • Returns all attributes of an item, or only the ones you want
    • Is eventually consistent by default but can request a consistent read
    • Can use conditional operators and filters to return precise results

DynamoDB Scans

  • Reads every item in the table and is operationally inefficient
  • Looks for all items and attributes in a table by default
  • Benefits;
    • Scans can apply filters to the results to refine vaules
    • Can return only specific attributes with the ProjectionExpression parameter
  • Negatives:
    • The larger the data set in the table the slower performance of a scan
    • The more filters on the scan the slower the performance
    • Returns only filtered results
    • Only eventually consistent reads are available

DynamoDB Scans – If you must use them

  • What you should keep in mind:
    • You can reduce Page Size of an operation with the Limit parameter, to limit how much data you try to retrieve at the same time
    • Avoid performing Scans on mission-critical tables
    • Program your application logic to retry any requests that recieves a response code saying that you exceeded provisioned throughput (or increase throughput)