Merge pull request #161 from davetownG/Issue-133-SocialNetwork-Add-READ.md

Issue 133 social network add read.md

Author: tebanieo

schema_design/SchemaExamples/SocialNetwork/README.md

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+# Social Network Data Modeling with Amazon DynamoDB
+
+## Overview
+
+This document outlines a use case using DynamoDB as a social network. A social network is an online service that lets different users interact with each other. The social network we'll design will let the user see a timeline consisting of their posts, their followers, who they are following, and the posts written by who they are following.
+
+## Key Entities
+
+1. user
+2. post
+
+## Design Approach
+
+We employ a single table design with the following key structure:
+
+- Partition Key (PK): Identifies the key entity type (u#<userID> for user, p#<postID> for post) and optionally, a second # followed by a descriptor of what is stored in the partition. 
+  - u#\<userID\> - Given user
+  - u#\<userID\>#follower - Given user's followers
+  - u#\<userID\>#following - The users that the given user is following
+  - u#\<userID\>#post - Given user's posts
+  - p#\<postID\>#likelist - The users that have liked the given post
+  - p#\<postID\>#likecount - The count of the given post's likes
+  - u#\<userID\>#timeline - Given user's timeline
+
+- Sort Key (SK): Contains the ID of an entity in the Partition Key collection 
+    **or** 
+  a descriptor of the attributes ("count", "info") for the primary key of \<PK\>\<SK\>
+
+    - Examples:  
+
+      | PK | SK | Sample Attributes |
+      | ----------- | ----------- | ----------- |
+      | u#12345 | `count` | follower#, following#, post# |
+      | u#12345 | `info` | name, content, imageUrl |
+      | u#12345#follower | u#34567 ||
+      | u#12345#following | u#34567 ||
+      | u#12345#post | p#12345 | content, imageUrl, timestamp |
+      | p#12345#likelist | u#34567 ||
+      | p#12345#likecount | `count` | etc |
+      | u#12345#timeline | p#34567#u#56789 | ttl |
+
+
+## Access Patterns
+
+The document covers 7 access patterns. For each access pattern, we provide:
+- Specific PK and SK used
+- Relevant DynamoDB operation (GetItem, Query)
+
+  | Access pattern | Operation | Partition key value | Sort key value |
+  | ----------- | ----------- | ----------- | ----------- |
+  | getUserInfoByUserID | Query | PK=\<userID\> |
+  | getFollowerListByUserID | Query | PK=\<userID\>#follower |
+  | getFollowingListByUserID | Query | PK=\<userID\>#following | 
+  | getPostListByUserID | Query | PK=\<userID\>#post |
+  | getUserLikesByPostID | Query | PK=\<postID\>#likelist |
+  | getLikeCountByPostID | GetItem | PK=\<postID\>#likecount |
+  | getTimelineByUserID | Query | PK=\<userID\>#timeline |
+
+## Goals
+
+- Model relationships between users and posts efficiently
+- Ensure scalability using Amazon DynamoDB's single table design principles
+
+## Schema Design
+
+A comprehensive schema design is included, demonstrating how different entities and access patterns map to the DynamoDB table structure. [SocialNetworkSchema.json](https://github.com/aws-samples/aws-dynamodb-examples/blob/master/schema_design/SchemaExamples/SocialNetwork/SocialNetworkSchema.json)
+
+## Additional Information
+[Social network schema design in DynamoDB](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/data-modeling-schema-social-network.html)