Update README.md with dataset structures

Author: Goshawk

README.md

@@ -1,17 +1,46 @@
 # datalake-worker
-Data lake implementation integrated with S3
+Data lake implementation integrated with AWS S3
 
 # Supported features
 
-- Async download a chunk from S3
+- Async-Download chunks from AWS S3
 - Persist on-disk in a lock-less manner
 - List all persisted chunks by ID from a cache
 - Find and lock a chunk - Once locked, chunk cannot be deleted
 - Scheduled deletion - Scheduled for deletion, a chunk will be removed once it is no longer in use.
 
-- Backend-agnostic datamanager. The RocksDB backend can be substituted with any in-process NoSQL or SQL storage engine.
+- Backend-agnostic datamanager. The RocksDB backend can be substituted with any in-process NoSQL or SQL storage engine.g
 
 
 # Design 
 
 ![image info](./design.png)
+
+# Datasource structure
+
+### Cache - in-memory map of chunks IDs to a lock permit
+
+| Chunk_ID    | Permit |
+| -------- | ------- |
+| 0x0A0B    |  0   |
+| 0x0A0C    | 1    |
+| 0x0A0C    | 0    |
+
+### OnDisk Tables and Indexes
+
+| Chunk_ID    | Encoded Chunk Data |
+| -------- | ------- |
+| 0x0A0B    |  0x..   |
+| 0x0A0C    | 0x...    |
+| 0x0A0C    | 0x    |
+
+| DatasetID_BlockNum   | Chunk_ID |
+| -------- | ------- |
+| 100_0    | 0x0A0B   |
+| 100_1    | 0x0A0B    |
+| 100_2    | 0x0A0B    |
+
+| Metadata    | Value |
+ | ---------| -------- |
+ 0x1 (Size_Key)    | 2000000 |
+