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Estimate the scale of the system you are going to design...
Define what APIs are expected from the system...
/api/users/register: Create a new user account./api/users/login: Authenticate user credentials./api/users/{user_id}: Fetch user profile details./api/posts/create: Submit a new post./api/posts/{post_id}: Retrieve a specific post./api/posts/{post_id}/vote: Upvote or downvote a post./api/posts/{post_id}: Remove a post./api/comments/create: Add a comment to a post./api/comments/{comment_id}: Retrieve a specific comment./api/comments/{comment_id}/vote: Upvote or downvote a comment./api/subreddits/create: Create a new subreddit./api/subreddits/{subreddit_id}: Retrieve subreddit details./api/subreddits/{subreddit_id}/moderators: Assign moderators to a subreddit./api/search: Search posts, comments, or subreddits./api/recommendations: Fetch personalized content recommendations./api/notifications: Retrieve user notifications./api/notifications/mark_as_read: Mark notifications as read.Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...
Usersuser_id (Primary Key): Unique identifier for each user.username: User’s chosen display name.email: User’s email address.password_hash: Hashed password.created_at: Timestamp of account creation.Postspost_id (Primary Key): Unique identifier for each post.user_id (Foreign Key): Associated user ID.subreddit_id (Foreign Key): Associated subreddit ID.content: Text content or media URL.votes: Upvote and downvote counts.created_at: Timestamp of post creation.Commentscomment_id (Primary Key): Unique identifier for each comment.post_id (Foreign Key): Associated post ID.user_id (Foreign Key): Associated user ID.content: Text content of the comment.votes: Upvote and downvote counts.created_at: Timestamp of comment creation.Subredditssubreddit_id (Primary Key): Unique identifier for each subreddit.name: Name of the subreddit.description: Description of the subreddit.created_at: Timestamp of subreddit creation.Notificationsnotification_id (Primary Key): Unique identifier for each notification.user_id (Foreign Key): Associated user ID.type: Type of notification (e.g., new comment, upvote).content: Notification details.created_at: Timestamp of notification creation.SearchIndexdocument_id: Identifier for posts, comments, or subreddits.type: Document type (e.g., post, comment, subreddit).content: Indexed content for search.metadata: Associated metadata (e.g., tags, votes).You should identify enough components that are needed to solve the actual problem from end to end. Also remember to draw a block diagram using the diagramming tool to augment your design. If you are unfamiliar with the tool, you can simply describe your design to the chat bot and ask it to generate a starter diagram for you to modify...
Manages user accounts, authentication, and roles. Provides functionalities for registration, login, and managing user profiles.
Handles subreddit creation, configuration, and moderation.
Manages user-generated content, including posts and threaded comments.
Tracks upvotes and downvotes for posts and comments.
Enables users to search for posts, comments, and subreddits, and provides personalized recommendations.
Manages notifications for user interactions, such as comments, replies, and private messages.
Supports community moderation by providing tools for reporting, reviewing, and removing inappropriate content.
Tracks platform activity and generates insights for admins and moderators.
Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...
Steps:
POST /api/users/register request with user details.Steps:
POST /api/subreddits/create request with subreddit details.Steps:
POST /api/posts/create request with the post details.Steps:
PUT /api/posts/{post_id}/vote request with the vote action.Steps:
GET /api/search request with query parameters.Steps:
POST /api/comments/create request with the comment details.Steps:
POST /api/posts/{post_id}/report request.Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...
The User Management Service manages user registration, authentication, and profile settings. When a user registers, the service validates input, hashes passwords using algorithms like bcrypt, and stores user details in the database. Authentication involves validating credentials, generating session tokens (e.g., JWT), and maintaining session metadata. Role-based access controls (RBAC) ensure user permissions for specific actions (e.g., moderating subreddits).
Implementation Example (Session Token Generation):
python
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import jwt
from datetime import datetime, timedelta
def generate_token(user_id):
payload = {
"user_id": user_id,
"exp": datetime.utcnow() + timedelta(hours=1)
}
return jwt.encode(payload, "secret_key", algorithm="HS256")
The Subreddit Management Service handles subreddit creation, configuration, and moderation. When a user creates a subreddit, the service validates the name, assigns default settings, and stores metadata in the database. Moderators can update rules and assign roles, ensuring subreddit-specific governance.
Implementation Example (RBAC for Moderation):
python
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class RBAC:
def init(self):
self.roles = {"admin": ["add_mod", "remove_post"], "mod": ["remove_post"]}
def has_permission(self, role, action):
return action in self.roles.get(role, [])
The Post and Comment Service manages user-generated content, including posts and threaded comments. When a post is submitted, it validates the subreddit ID, processes content (e.g., sanitizing HTML), and stores it in the database. Threaded comments are represented using parent-child relationships.
Implementation Example (Hotness Algorithm):
python
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import math
from datetime import datetime
def calculate_hotness(score, created_at):
order = math.log(max(abs(score), 1), 10)
seconds = (created_at - datetime(1970, 1, 1)).total_seconds()
return order + seconds / 45000
The Voting Service tracks upvotes and downvotes for posts and comments. It ensures idempotency (one vote per user per item) and updates content ranking in real time.
Implementation Example (Vote Tracking):
python
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class VoteTracker:
def init(self):
self.votes = {}
def cast_vote(self, user_id, post_id, vote):
self.votes[(user_id, post_id)] = vote
The Search and Discovery Service indexes posts, comments, and subreddits for fast retrieval. It uses Elasticsearch for full-text search and relevance ranking. Personalized recommendations are generated using collaborative filtering.
Implementation Example (Inverted Index Search):
python
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class InvertedIndex:
def init(self):
self.index = {}
def add_document(self, doc_id, terms):
for term in terms:
self.index.setdefault(term, []).append(doc_id)
Explain any trade offs you have made and why you made certain tech choices...
Microservices Architecture:
NoSQL for Posts and Comments:
Redis for Caching:
Inverted Index for Search:
Try to discuss as many failure scenarios/bottlenecks as possible.
Content Moderation Overload:
Vote Manipulation:
High Query Load on Search:
Database Overload:
Cache Inconsistency:
What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?
Advanced Recommendation System:
Real-Time Content Moderation:
Geographic Data Replication:
Dynamic Autoscaling:
Robust Search Optimizations: