REST API & Webhooks

REST APIs and webhooks are the two most commonly used integration patterns in modern production environments. They solve the same fundamental problem – systems need to exchange data – but in opposite ways.

A REST API follows the pull principle: one system actively requests data and receives a response. Typical for queries like "give me the current order data" or "write this confirmation back to the ERP."

A webhook follows the push principle: a system proactively notifies another system when an event has occurred – without the recipient needing to poll continuously. Typical for events like "order started," "batch quarantined," or "critical fault triggered."

In robust integrations, both are combined: the webhook acts as the trigger, the REST API retrieves the full details.

Typical Use Cases in Manufacturing

REST APIs are used for pulling order data from ERP into MES, posting confirmations for quantities, times, and scrap, exchanging data between MES and QMS or LIMS, and delivering defined report exports to BI systems.

Webhooks are the right pattern when events need to be distributed in near-real-time: order started or completed, batch quarantined or released, critical fault occurred, recipe changed, or shift report available.

Advantages and Limitations

REST APIs offer strong controllability and debuggability – every request is traceable. They work well for status data and scenarios with clear data ownership. Their limitation: heavy polling creates system load, and near-real-time behavior requires high request frequency.

Webhooks react faster than polling and cleanly decouple events from reactions. Their limitation: delivery is not automatically guaranteed – retries, idempotency, and ordering must be explicitly planned. Security requirements (HMAC signatures, TLS, token validation) are non-negotiable.

What Actually Matters in Integration

Regardless of the pattern chosen, six factors determine integration stability in practice: a clear source-of-truth definition for each data type, idempotency on the receiver side so duplicate events cause no harm, a defined retry strategy for outages, active monitoring for silent failures and missing events, a versioning strategy for payload changes, and consistent security with auth tokens, IP restrictions, and encrypted connections.

Decision Guide

For status data with moderate change frequency, REST is the right choice. For reacting quickly to events, webhooks are the right pattern. For both – which is the norm in manufacturing – combine them: webhook as trigger, REST for detail data.

Common Mistakes

Webhooks without retry logic and idempotency lead to duplicate bookings and inconsistent states. REST with aggressive polling creates unnecessary load and unstable integrations. Missing ownership definitions cause systems to overwrite each other. No observability means the integration "works" – until it quietly stops working.

FAQ

Can REST API and webhooks be used together? Yes, and this is the recommended practice. The webhook signals that something has happened. The REST API delivers the complete, current dataset. Both patterns complement each other.

Is a REST API the same as a web API? Not necessarily. REST (Representational State Transfer) is an architectural style for HTTP-based interfaces. Web API is a more general term – REST APIs are a widely used form of it, but not the only one.

What is the difference between webhooks and message queues like Kafka? Webhooks are simple HTTP push notifications, sent directly from system to system. Message queues like Apache Kafka are dedicated event brokers with persistence, replay capability, and scalable routing. For high event volumes or multi-consumer scenarios, message queues are the more robust choice.

How should webhooks be secured? The minimum standard includes HMAC signatures for sender verification, TLS encryption for the connection, token-based authentication, and optionally IP allowlisting. Unsecured webhooks are a relevant security risk in OT/IT environments.