# Reference and Support

Reference material is collected here.

| Content | Description |
| --- | --- |
| [Architecture](../introduction/architecture.md) | The core data model, southbound-to-northbound routing, the stream processing engine, and offline caching |
| [HTTP API](../api/api.md) | Authentication, data types, driver and application settings, and error codes for the REST API |
| [Performance](../performance/performance.md) | Measured tag counts and resource usage for the Modbus TCP, OPC UA, and Siemens S7 drivers |
| [FAQ](../faq/faq_basic.md) | Common questions on deployment, limits, and protocol support |
| [Release History](../release_history/release_history.md) | New features and fixes per version |

For stream processing SQL syntax, functions, and windows, see [Data Processing · SQL Reference](../streaming-processing/sqls/overview.md). For name lengths, group limits, and the minimum polling interval of a single instance, see [Data Collection, Processing and Delivery · Configuration specification](../configuration/introduction.md#configuration-specification).