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Notes on DynamoDB

Amazon DynamoD is a

  • Fully managed NoSQL database service

  • Provides consistent, single-digit millisecond latency at any scale.

  • Supports both document and key-value data model

  • Its flexible data model and reliable performance make it a great fit for mobile, web, gaming, ad-tech, IoT etc.

  • Stored on SSD Storage

  • Spread Across 3 geographically distinct data centers

  • Eventual Consistent Read (Default)

    • Consistency across all copies of data is usually reached within a second. Repeating a read after a short amount of time should return the updated data. (Best Read Performance)

  • Strongly Consistent Reads

    • A stronly consistent read returns a result that reflects all writes that received a successful response prior to the read.

NOTE: Super easy to scale! Push button scaling

DynamoDB Pricing

Pricing is based on provision throughput capacity

  • Write Throughput $0.0065 per hour for every 10 units
  • Read Throughput $0.0065 per hour for every 50 units
  • Storage costs of $0.25G per month

Pricing Example:

Constraint: 1 million WRITEs and 1 million READs per day, while storing 3G of data.

First, calculate how many writes and reads per second you need.

1 million evenly spread writes per day is equivalent to 1,000,000 (writes) /24 (hours) / 60 (minutes) / 60 (seconds) = 11.6 writes per second.

-- BREAKDOWN --

DynamoDB WRITE Capacity Unit - 1 per second = 12
DynamoDB READ Capacity Unit - 1 per second = 12

READ Capacity Units - billed in blocks of 50
WRITE Capacity Units - billed in blocks of 10

Calc WRITE Capacity Units = (0.0065 / 10) x 12 x 24 = $0.1872
Calc READ Capacity Units = (0.0065 / 10) x 12 x 24 = $0.0374

My curated list of FAQs on AWS DynamoDB

What is partition key?

The primary key is made up of a partition key (hash key) and an optional sort key. The partition key is used to partition data across hosts for scalability and availability. Choose an attribute which has a wide range of values and is likely to have evenly distributed access patterns. For example CustomerId is good while GameId is bad if most of your traffic relates to a few popular games.

What is sort key?

The sort key allows for searching within a partition. For example, an Orders table with primary attribute CustomerId and sort attribute OrderTimestamp would allow for queries for all orders by a specific customer in a given date range.

DynamoDB default setting

  • No secondary indexes.
  • Provisioned capacity set to 5 reads and 5 writes.
  • Basic alarms with 80% upper threshold using SNS topic "dynamodb".
  • Encryption at Rest with DEFAULT encryption type

Sample record

[
  {
    "status": "PROCESSING",
    "text": "Hello Cloud Gurus!",
    "voice": "Joanna",
    "id": "d97e244c-0b49-4374-aa7a-fbf30c36dd17"
  },
  {
    "status": "PROCESSING",
    "text": "Hello Cloud Gurus!",
    "voice": "Joanna",
    "id": "267dad5f-2488-4457-bf14-8eff6d4b7ac6"
  }
]

DynamoDB vs MongoDB