> For the complete documentation index, see [llms.txt](https://docs.tpi.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tpi.dev/overview/apim-architecture.md).
# APIM Architecture
Self-hosted architecture refers a scheme where all digiRunner API Management components are hosted by the user on-prem and/or in a private cloud.
## Common HTTP API Call Structure
In this structure, the user accesses various services directly via the browser using HTTP or HTTPS protocols. Each service is exposed directly to the browser, meaning any changes to the API paths or services require modifications on the client side.
Without a centralized API management tool, limiting and monitoring client traffic becomes challenging, potentially leading to service overload. Additionally, since APIs are exposed without a centralized gateway or proxy to manage access, the risk of security vulnerabilities increases, including threats like DDoS attacks or unauthorized access.
## APIM HTTP API Call Structure
Unlike the previous structure, this setup introduces an API Management layer (APIM), represented by digiRunner, which acts as a proxy between the browser and the backend services. This approach abstracts the direct connection between the browser and the services, providing centralized control and easier API management.
When backend APIs change, only the gateway (APIM) requires adjustment, eliminating the need for changes on the client side and improving flexibility. Furthermore, the API management layer functions as a firewall, offering security features such as authentication, authorization, and rate-limiting, which help prevent unauthorized access and protect against malicious attacks.
Since all API requests are routed through the APIM, it allows for unified traffic management, setting request limits and priorities, preventing individual services from being overloaded. When new services or features need to be added, routing or services can be configured within the APIM without altering the client logic, making scaling significantly more convenient.
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