Webhooks vs Polling: Approaches for Backend-Frontend Communication in Modern Applications
Effective backend-to-frontend communication is essential when building web applications, especially when different services need to keep data synchronized across platforms, whether on iOS, Android, or the web
Typically, an API facilitates this data transfer, managing requests for data based on specific needs. However, relying solely on explicit API calls can lead to outdated information on the user interface since data changes on the backend are often unknown until the frontend initiates a request.
This article explores two key approaches — Polling and Webhooks — for designing API communication strategies that keep the frontend updated as soon as backend data changes.
Polling
Polling is a technique where the client repeatedly sends requests to the server at regular intervals to check for updates. The interval may vary based on the use case, but the goal is to strike a balance between frequency and data freshness.
Example Use Case: Imagine a news feed application where updates are expected frequently but are not continuous. The client can poll the server every few minutes to display new articles.
Advantages of Polling
Simplified Security: Since polling does not require a public endpoint, there is minimal exposure, reducing vulnerability to external threats.
Controlled Requests: The client dictates the polling interval, allowing for flexibility in resource management.
Reduced Client Complexity: No additional client-side authentication or authorization logic is needed for specific endpoints, as each poll is handled as a standard request.
Disadvantages of Polling
Resource-Intensive: Polling is often inefficient as it frequently requests data regardless of changes, potentially leading to wasted server resources.
Unreliable Freshness: Since polling happens at fixed intervals, the client may not always reflect the latest changes immediately, especially if data changes between requests.
Long Polling
Long Polling is a variation of standard polling designed to improve data freshness without continuously requesting updates. The client sends a request to the server and keeps the connection open until the server has new data to send back or the request times out. Once a response is received, the client immediately initiates a new request, repeating the process.
Example Use Case: Chat applications frequently use long polling to ensure messages appear as soon as they’re received.
Advantages of Long Polling
Near Real-Time Updates: By keeping the connection open, long polling provides updates almost as soon as data changes occur.
Efficient Resource Usage: Compared to traditional polling, long polling reduces redundant requests, lowering the resource overhead on the server.
Disadvantages of Long Polling
Server Load: Long polling can lead to increased server load due to many open connections, especially if many clients connect simultaneously.
Higher Complexity: Implementing long polling requires managing multiple open requests, which can complicate server and client logic.
Webhooks
Webhooks provide an event-driven approach where the server actively notifies the client about changes by sending HTTP POST requests to a client-designated URL. This “push” approach allows for real-time updates without the need for frequent client-initiated requests.
Example Use Case: Webhooks are ideal for events requiring instant notifications, such as payment confirmations, inventory updates, or automated workflows.
Advantages of Webhooks
Immediate Data Updates: Since the server pushes changes to the client as soon as they happen, data on the frontend remains fresh.
Scalability for Multiple Systems: Multiple clients can listen to the same webhook, ensuring that all subscribed systems receive updates concurrently and stay synchronized.
Reduced API Call Frequency: With event-driven updates, unnecessary API calls are minimized, lowering bandwidth and server costs.
Disadvantages of Webhooks
Complex Setup: Setting up webhooks involves exposing endpoints that require secure authentication and authorization, adding complexity to the setup process.
Endpoint Security Risks: Since webhooks expose a public endpoint, they require careful security handling to prevent unauthorized access.
When to Use Polling vs. Webhooks
Polling works best when:
Real-time updates are not critical, and data can tolerate delays.
The backend cannot actively send updates or when webhook setup is not feasible.
The client prefers control over when and how often it checks for updates.
Webhooks are ideal for:
Scenarios where instant updates are essential, such as user notifications, transactions, or status updates.
Situations where multiple systems need simultaneous updates.
Cases where API usage costs or server load are a concern and need to be minimized.
Conclusion
Both Polling and Webhooks have their unique strengths and limitations. Polling allows the client to control the request rate, although it is resource-intensive and may lead to stale data. Webhooks provide immediate, real-time data but require a more complex setup and careful security considerations.
When choosing between polling and webhooks, consider factors such as update frequency, resource constraints, and the importance of data freshness to deliver an optimal user experience.
About The Author
Apoorv Tomar is a seasoned software developer. You can connect on social networks. Subscribe to the newsletter for the latest curated content.
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