bit of backend structure

Rewritten-docs.md

@@ -257,11 +257,37 @@ one purpose: evaluate user’s solutions of their assignments.
 
 @todo: describe the outputs of the Backend
 
+@todo: describe how the backend receives the inputs and how it
+communicates the results
+
+## Components
+
+Whole backend is not just one service/component, it is quite complex system on its own.
+
 @todo: describe the inner parts of the Backend (and refer to the Wiki
 for the technical description of the components)
 
-@todo: describe how the backend receives the inputs and how it
-communicates the results
+### Broker
+
+@todo: gets stuff done, single point of failure and center point of ReCodEx universe
+
+### Fileserver
+
+@todo: stores particular datas from frontend and backend, hashing, HTTP API
+
+### Worker
+
+@todo: describe a bit of internal structure in general
+
+@todo: describe how jobs are generally executed
+
+### Monitor
+
+@todo: not necessary component which can be ommited, proxy-like service
+
+## Backend internal communication
+
+@todo: internal backend communication, what communicates with what and why
 
 The Frontend
 ============