Webhooks vs Polling vs Event-Driven Integrations

When synchronizing state between business systems—such as propagating an order from an e-commerce platform to an ERP, or alerting a mobile app of a verified payment—choosing the communication pattern determines network efficiency, infrastructure cost, and data freshness.

The three primary integration mechanisms are Periodic Polling, Outbound Webhooks (Push), and Event-Driven Streaming (Pub/Sub).

POLLING (Pull):
Consumer --- [GET /api/orders?since=12:00] ---> Provider (Returns 0 results)
Consumer --- [GET /api/orders?since=12:05] ---> Provider (Returns 0 results)
Consumer --- [GET /api/orders?since=12:10] ---> Provider (Returns 1 new order)

WEBHOOKS (Push):
Provider (Order Created) --- [POST https://consumer.com/webhook] ---> Consumer

EVENT STREAMING (Pub/Sub):
Publisher ---> [Kafka / RabbitMQ Topic: "orders.created"] ---> Multiple Consumers

Architectural Comparison Matrix#

1. The True Cost of Polling#

While polling is straightforward to implement, it incurs massive waste at scale. A system polling 10,000 partner records every 60 seconds generates 14.4 million HTTP requests per day, even if only 20 records changed. This exhausts database connections and triggers unnecessary compute costs.

2. Engineering Outbound Webhooks for Enterprise Reliability#

Outbound webhooks deliver immediate notifications but introduce distributed failure risks. A robust webhook engine must implement:

• Cryptographic Signatures: Attaching an X-Signature-SHA256 computed from the payload and shared secret to prevent spoofing.
• Timestamp Nonces: Including X-Timestamp to prevent replay attacks.
• Exponential Backoff with Jitter: Retrying failed HTTP 5xx responses over a 24-hour window (e.g. at 1m, 5m, 30m, 2h, 8h).
• Dead-Letter Queues (DLQ): Allowing administrators to manually inspect permanently failed webhook deliveries and replay them after endpoint fixes.

// Dispatching signed webhook in Alegor Integrations Module
class WebhookDispatcher
{
    public function dispatch(WebhookEndpoint $endpoint, string $event, array $payload): void
    {
        $timestamp = time();
        $jsonPayload = json_encode([
            'id' => Str::uuid()->toString(),
            'event' => $event,
            'timestamp' => $timestamp,
            'data' => $payload,
        ]);

        $signature = hash_hmac('sha256', "{$timestamp}.{$jsonPayload}", $endpoint->secret);

        Http::timeout(5)
            ->withHeaders([
                'Content-Type' => 'application/json',
                'X-Alegor-Signature' => $signature,
                'X-Alegor-Timestamp' => (string) $timestamp,
                'User-Agent' => 'Alegor-Webhook-Engine/2.0',
            ])
            ->post($endpoint->url, json_decode($jsonPayload, true));
    }
}

3. When to Use Event Streaming (Kafka / RabbitMQ)#

Webhooks are ideal for B2B external integrations where partners manage their own web servers. For internal, high-throughput microservices or asynchronous micro-tasks within your own infrastructure, internal event brokers (RabbitMQ / Redis Streams / Kafka) provide higher throughput, exactly-once delivery guarantees, and backpressure management without HTTP overhead.

Explore the Alegor Integrations Module or read How to Design Reliable Integrations.