Requirements

Functional Requirements:

• Tag Creation
  • the user should be able to create tag for item

• Tag Assignment
  • the user should be able to assign tag to item

• Tag Deletion
  • the user should be able to delete tag

• Tag Removal
  • the user should be able to remove tag from items in the system

• Tag Search
  • the user should be able to search item based on tags

• Tag Normalization
  • the system must be able to merge similar tag together

• Tag Suggestion
  • the system must be able to suggest tag for the item

Non-Functional Requirements:

• Low Latency
  • the response time should be < 100 ms

• High Availability
  • 99.99% up time

• Scalability
  • able to handle 23.1481 reqs/s during normal load
  • able to handle more than 231.481 reqs/s during peak time

• Durability
  • the relationship between tags and items must be retained until deleted

• Consistency
  • every user got the same data eventually

Capacity Estimation

• Assumption
  • Total users: 1,000,000 users
  • Active users per day: 10,000
  • Each user make 200 requests/day

• Load
  • in average there is about 200 * 10,000 = 2,000,000 requests/day
  • hence average rps = 2,000,000 / (60*60*24) = 23.1481481481 reqs/s
  • can peak at 231.1481 reqs/s

• Storage usage
  • tags
    • each tag take 50 bytes of space
    • there can be a billion of tags
    • take 50 GBs
  • items
    • image only
    • there can be a billion of items
    • each item take 1 KB in average
    • take 1 TB
  • we need about 1.5 TB
  • 2x error factor -> we need about 3 TBs

API Design

External API

1.Tag Creation

• Method: POST
• endpoint: /{version}/tag
• body:
  • tag_name: str
• response
  • Create new tag success
    • status_code: int: 200
    • status: ENUM: SUCCESS
    • tag_id: id: new tag id

• • Duplicate tag
    • status_code: int: 409
    • status: ENUM: ERROR
    • message: str: can't create duplicate tag

• • Bad Request
    • status_code: int: 50x
    • status: ENUM: ERROR
    • message: str: something went wrong at the backend.

2.Tag Assignment

• Method: PATCH
• Endpoint: /version/item/{item_id}/addTags
• Path Variables:
  • item_id: id: item's id
• Body:
  • tag_ids: list[id]: ids of tag added.
• response
  • Assigning Succeeded:
    • status_code: int: 200
    • status: ENUM: SUCCESS
  • Duplicate Tag
    • status_code: int: 409
    • status: ENUM: ERROR
    • message: str: this item already had this tag
  • Item Not Found
    • status_code: int: 404
    • status: ENUM: ERROR
    • message: str: item not found
  • Bad Request:
    • status_code: int: 50x
    • status: ENUM: ERROR
    • message: str: something went wrong at the backend.

3.Tag Deletion

• METHOD: DELETE
• endpoint: /{version}/tag/{tag_id}
• Path Variables:
  • tag_id: id: id of tag that need to be deleted
• Response:
  • Delete Success:
    • status_code: int: 200
    • status: ENUM: SUCCESS
  • Used Tagged:
    • status_code: int: 460
    • status: ENUM: ERROR
    • message: str: this tag is currently being used.
  • Service Unavailable:
    • status_code: int: 503
    • status: ENUM: ERROR
    • message: str: backend went down

4.Tag Removal

• METHOD: PATCH
• Endpoint: /{version}/item/{item_id}/delTags
• Path Variable:
  • item_id: id: item's id
• Body:
  • tag_ids: list[id]: ids of tag that need to be delted
• Response:
  • Remove Succeeded:
    • status_code: int: 200
    • status: ENUM: SUCCESS
  • Item Not Found:
    • status_code: int: 404
    • status: ENUM: ERROR
    • message: str: item not found
  • Service Unavailable:
    • status_code: int: 503
    • status: ENUM: ERROR
    • message: str: backend went down

5.Tag Suggestion

• Method: GET
• Endpoint: /{version}/suggest_tag/{item_id}
• Path Variables:
  • item_id: id: id of item
• Response:
  • Success:
    • status_code: int: 200
    • status: ENUM: SUCCESS
    • suggested_tags: list[id]: list of tag id suggest by our system
  • Service Unavailable:
    • status_code: int: 503
    • status: ENUM: ERROR
    • message: str: backend went down

6.Tag Search

• Method: GET
• Endpoint: /{version}/search?tag1={tag_1}&tag2={tag_2} ...
• Query Variable:
  • tag: str: tag's name that used as filter
• Success:
  • status_code: int: 200
  • status: ENUM: SUCCESS
  • items: list[item]: list of item that satisfied the condition

Internal API

1.Tag Normalization

• METHOD: POST
• Endpoint: /{version}/normalize
• Body:
  • tag_name: str: tag's name
• Response:
  • New Tag:
    • status_code: int: 200
    • status: SUCCESS
    • new_tag: bool: true
    • tag_name: str: tag's name

• • Existed Tag:
    • staus_code: int: 200
    • status: SUCCESS
    • new_tag: bool: false
    • tag_name: str: tag's name

High-Level Design

Describe the overall system architecture. Identify the main components needed to solve the problem end-to-end. Use the diagramming tool to create a block diagram.

Detailed Component Design

Deep dive into 2-3 key components. Explain how they work, how they scale, discuss tradeoffs, capacity, and any relevant algorithms or data structures.