Design: Trading Card Pricing Tracking System

Data Collection and Storage

• Users, Holdings, and Products: These entities can be stored in DynamoDB.
• Market Transactions: Store market transaction data in DynamoDB as well.

Market Data Aggregation

• Collect data from various market sources using APIs or web scraping.
• Process and clean the collected data before storing it in DynamoDB.
• Utilize AWS Lambda functions or EC2 instances for data processing.

Price Deviation Calculation

• Implement a background job or scheduled Lambda function to calculate the average market price for each product.
• Store average market price alongside product details in DynamoDB.
• Calculate user-defined threshold (e.g., +/- 10%) based on the average market price.

Listing Monitoring and Notification

• Use DynamoDB Streams to capture changes in the listings table.
• Set up an AWS Lambda function to analyze changes and compare listed prices with average market price and threshold.
• Publish notification message to an SNS topic when a listing price exceeds the threshold.

Notification Service

• Create an SNS topic and subscribe users to it.
• Configure SNS to send notifications via multiple communication channels.
• Integrate Amazon SES with SNS to send emails for notifications.

Diagram

          +------------------------+
          |        Users           |
          +------------------------+
                    |        +
                    |        | Manages
                    |        |
          +------------------------+
          |       Holdings         |
          +------------------------+
                    |        +
                    |        | Consists of
                    |        |
          +------------------------+
          |       Products         |
          +------------------------+
                    |        +
                    |        | Contains
                    |        |
          +------------------------+
          |   Market Transactions   |
          +------------------------+
                    |
                    |  Collects from
                    |
          +------------------------+
          |  Market Data Aggregator|
          +------------------------+
                    |
                    |  Calculates and updates
                    |
          +------------------------+
          | Price Deviation Service|
          +------------------------+
                    |
                    |  Monitors and publishes
                    |
          +------------------------+
          |     DynamoDB Streams    |
          +------------------------+
                    |
                    |  Analyzes changes and publishes
                    |
          +------------------------+
          |     Lambda Function     |
          +------------------------+
                    |
                    | Subscribes and sends
                    |
          +------------------------+
          |      SNS (Topic)        |
          +------------------------+
                    |        +
                    |        | Sends
                    |        |
          +------------------------+
          |        SES             |
          +------------------------+

Advantages of using DynamoDB, SNS, and SES:

• DynamoDB provides scalability, low latency, and automatic scaling.
• SNS offers a flexible and scalable notification service.
• SES ensures reliable email delivery.