Debug This Architecture

Potential Failure Modes, Race Conditions, and Scaling Bottlenecks

1. WebSocket Connection Failures:

   • Failure Mode: WebSocket connections can drop due to network issues or server crashes.
   • Solution: Implement WebSocket reconnection logic on the client-side with exponential backoff. On the server-side, ensure that WebSocket servers are stateless and can be easily restarted without losing state.
   • Trade-offs: Increased complexity in client-side code and potential delay in reconnection.

2. Single Point of Failure in PostgreSQL:

   • Failure Mode: PostgreSQL could become a single point of failure if it goes down.
   • Solution: Use PostgreSQL replication (master-slave setup) and automatic failover mechanisms. Consider using a managed database service that offers high availability.
   • Trade-offs: Increased cost and complexity in managing replication and failover.

3. Race Conditions in Conflict Resolution:

   • Failure Mode: Race conditions can occur when multiple users edit the same paragraph simultaneously, leading to data inconsistency.
   • Solution: Implement Operational Transformation (OT) or Conflict-free Replicated Data Types (CRDTs) for more sophisticated conflict resolution.
   • Trade-offs: Increased complexity in the conflict resolution logic and potential performance overhead.

4. Polling Overhead:

   • Failure Mode: Polling PostgreSQL every 2 seconds can create significant load on the database, especially as the number of servers scales.
   • Solution: Use Redis as a message broker to publish changes to all servers instead of polling. Each server subscribes to a Redis channel for document changes.
   • Trade-offs: Additional infrastructure and complexity in managing Redis.

5. JWT Token Expiry and Security:

   • Failure Mode: JWT tokens stored in localStorage can be vulnerable to XSS attacks, and their expiry can cause frequent re-authentication.
   • Solution: Use HTTP-only cookies for storing JWT tokens to mitigate XSS risks. Implement token refresh mechanisms to avoid frequent re-authentication.
   • Trade-offs: Increased complexity in managing token refresh and potential security risks if not implemented correctly.

6. CDN Caching Issues:

   • Failure Mode: Caching API responses for 5 minutes can lead to stale data being served to users.
   • Solution: Implement cache invalidation strategies based on document changes. Use shorter cache durations for more frequently updated documents.
   • Trade-offs: Increased complexity in cache management and potential performance overhead due to more frequent cache invalidations.

7. Scaling Bottlenecks in WebSocket Servers:

   • Failure Mode: As the number of WebSocket connections grows, the load on individual servers can become a bottleneck.
   • Solution: Use a WebSocket gateway or a message broker (e.g., Redis Pub/Sub) to distribute WebSocket connections across multiple servers.
   • Trade-offs: Increased complexity in managing WebSocket connections and potential latency due to message brokering.

8. Document Partitioning Issues:

   • Failure Mode: Document partitioning by organization ID can lead to hotspots if certain organizations have significantly more documents.
   • Solution: Implement a more granular partitioning strategy, such as partitioning by document ID or using a sharding strategy based on document metadata.
   • Trade-offs: Increased complexity in partitioning logic and potential performance overhead due to more frequent partitioning operations.

Summary of Solutions and Trade-offs

1. WebSocket Connection Failures:

   • Solution: WebSocket reconnection logic with exponential backoff.
   • Trade-offs: Increased client-side complexity and potential delay in reconnection.

2. Single Point of Failure in PostgreSQL:

   • Solution: PostgreSQL replication and automatic failover.
   • Trade-offs: Increased cost and complexity in managing replication and failover.

3. Race Conditions in Conflict Resolution:

   • Solution: Implement Operational Transformation (OT) or CRDTs.
   • Trade-offs: Increased complexity in conflict resolution logic and potential performance overhead.

4. Polling Overhead:

   • Solution: Use Redis as a message broker.
   • Trade-offs: Additional infrastructure and complexity in managing Redis.

5. JWT Token Expiry and Security:

   • Solution: Use HTTP-only cookies and token refresh mechanisms.
   • Trade-offs: Increased complexity in managing token refresh and potential security risks.

6. CDN Caching Issues:

   • Solution: Implement cache invalidation strategies.
   • Trade-offs: Increased complexity in cache management and potential performance overhead.

7. Scaling Bottlenecks in WebSocket Servers:

   • Solution: Use a WebSocket gateway or message broker.
   • Trade-offs: Increased complexity in managing WebSocket connections and potential latency.

8. Document Partitioning Issues:

   • Solution: Implement a more granular partitioning strategy.
   • Trade-offs: Increased complexity in partitioning logic and potential performance overhead.

By addressing these issues, the architecture can become more robust, scalable, and secure, ensuring a better user experience in a real-time collaborative document editor.