diff --git a/README.md b/README.md
index 14ecadc..0cc8245 100644
--- a/README.md
+++ b/README.md
@@ -33,3 +33,33 @@ For end users door can be opened by:
 For emergency cases:
 
 * Log into door controller via SSH and issue `killall -sUSR1 godoor`
+
+# Door system architecture
+
+* Web UI / Slack commands - https://git.k-space.ee/k-space/inventory-app
+* Card List provider - https://git.k-space.ee/k-space/doorboy-proxy
+
+```
+                               ┌──────────────┐     
+┌──────────────────┐           │ Card Reader  │  ...
+│ Slack /open-door │           └───────┬──────┘     
+└─────────────────┬┘                   │            
+                  │            ┌──────────────┐     
+┌──────────────┐  │       ┌────│ RPI/w godoor │  ...
+│ Web Open door│  │       │    └──────────────┘     
+└─────────┬────┘  │       │Swipe   ▲                
+          │       │       │Event   │ Open event     
+          ▼       ▼       ▼        │ Card list      
+    ┌───────────────┐    ┌─────────┴─────┐          
+    │ inventory-app │    │ doorboy-proxy │          
+    │ doorboy.py    │    └───────────────┘          
+    └───────────────┘          ▲                    
+              │                │                    
+              │                │                    
+              │                ▼                    
+              │           ┌───────────┐             
+              └──────────►│  MongoDB  │             
+                          └───────────┘             
+```
+
+https://asciiflow.com/ diagram