WebSockets vs Webhooks
Reacting to real-time events from Avalanche smart contracts allows for immediate responses and automation, improving user experience and streamlining application functionality. It ensures that applications stay synchronized with the blockchain state.
There are two primary methods for receiving these on-chain events:
- WebSockets, using libraries like Ethers.js or Viem
- Webhooks, which send structured event data directly to your app via HTTP POST.
Both approaches enable real-time interactions, but they differ drastically in their reliability, ease of implementation, and long-term maintainability. In this post, we break down why Webhooks are the better, more resilient choice for most Avalanche developers.
Architecture Overview
The diagram below compares the two models side-by-side: WebSockets
- The app connects to the Avalanche RPC API over WSS to receive raw log data.
- It must decode logs, manage connection state, and store data locally.
- On disconnection, it must re-sync via an external Data API or using standard
eth_*
RPC calls (e.g.,eth_getLogs
,eth_getBlockByNumber
).
eth_subscribe
, which requires node support.Webhooks
- The app exposes a simple HTTP endpoint.
- Decoded event data is pushed directly via POST, including token metadata.
- Built-in retries ensure reliable delivery, even during downtime.
eth_*
calls to recover older missed events.Using WebSockets: Real-time but high maintenance
WebSockets allow you to subscribe to events using methods like eth_subscribe. These subscriptions notify your app in real-time whenever new logs, blocks, or pending transactions meet your criteria.
The downside? If your connection drops, you lose everything in between. You’ll need to:
- Set up a database to track the latest processed block and log index.
- Correctly handling dropped connections and reconnection by hand can be challenging to get right.
- Use
eth_getLogs
to re-fetch missed logs. - Decode and process raw logs yourself to rebuild app state. This requires extra infrastructure, custom recovery logic, and significant maintenance overhead.
Webhooks: Resilient and developer-friendly
Webhooks eliminate the complexity of managing live connections. Instead, you register an HTTP endpoint to receive blockchain event payloads when they occur.
Webhook payload example:
You get everything you need:
- Decoded event data
- Token metadata (name, symbol, decimals)
- Full transaction context
- No extra calls. No parsing. No manual re-sync logic.
Key Advantages of Webhooks
- Reliable delivery with zero effort: Built-in retries ensure no missed events during downtime
- Instant enrichment: Payloads contain decoded logs, token metadata, and transaction context
- No extra infrastructure: No WebSocket connections, no DB, no external APIs
- Faster development: Go from idea to production with fewer moving parts
- Lower operational cost: Less compute, fewer network calls, smaller surface area to manage
If we compare using a table:
Feature | WebSockets (Ethers.js/Viem) | Webhooks | ||
---|---|---|---|---|
Interruption Handling | Manual; Requires complex custom logic | Automatic; Built-in queues & retries | ||
Data Recovery | Requires DB + External API for re-sync | Handled by provider; No re-sync logic needed | ||
Dev Complexity | High; Error-prone custom resilience code | Low; Focus on processing incoming POST data | ||
Infrastructure | WSS connection + DB + Potential Data API cost | Application API endpoint | ||
Data Integrity | Risk of gaps if recovery logic fails | High; Ensures eventual delivery | ||
Payload | Often raw; Requires extra calls for context | Typically enriched and ready-to-use | ||
Multiple addresses | Manual filtering or separate listeners per address | Supports direct configuration for multiple addresses | ||
Listen to wallet addresses | Requires manual block/transaction filtering | Can monitor wallet addresses and smart contracts |
Summary
- WebSockets offer real-time access to Avalanche data, but come with complexity: raw logs, reconnect logic, re-sync handling, and decoding responsibilities.
- Webhooks flip the model: the data comes to you, pre-processed and reliable. You focus on your product logic instead of infrastructure.
- If you want to ship faster, operate more reliably, and reduce overhead, Webhooks are the better path forward for Avalanche event monitoring.
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