readme update

README.md

@@ -1,16 +1,44 @@
-# Transactions calculator
+# Transactions processor
 
-## Build
+## Dependencies
 
-```
-cargo build [--release]
-```
+- **tokio && tokio_stream**: Async runtime that allows us to solve the problem
+  using concurrency and streams
+- **csv_async**: Thanks to tokio_stream and this library we can read the CSV
+  files using streams instead of writting the entire CSV on memory
+- **serde**: This library offers an awesome api to easily convert strings to
+  structured data.
+- **thiserror & anyhow**: I like to use this libraries to handle errors on a
+  cleaner way.
+- **async-trait**: Since we implement the AsyncActor trait we need to use this
+  library so rust can compile traits using async methods
 
-## Run
+## Architecture
 
-```
-cargo run
-```
+This project is based on the Actor Model.
+
+- Each actor run on its own thread (tokio tasks in this case)
+- Actors do not share state
+- Actors just receive messages and react to it
+- Each actor has a mailbox (queue) from which it reads the messages in order.
+
+### TxProcessor actor
+
+This actor is responsible for processing `Transaction` objects, spawn new
+Account actors if needed and send messages to them telling to perform any
+action.
+
+### Account actor
+
+This actor is responsible for managing an `Account` object and a map of the
+transactions done on that account.
+
+### Why this architecture?
+
+The Actors model offers a simple, clean and scalable way of building concurrent
+systems. Because each actor owns its own resources without sharing it to the
+outside world there is no need to use common concurrent techniques such as Locks
+and it ensures to not have data races.
 
 ## Author