update prefix store environment variables info in documentation

Signed-off-by: Maya Barnea <mayab@il.ibm.com>

Author: mayabar

docs/architecture.md

@@ -81,7 +81,7 @@ These components are maintained in the `llm-d-inference-scheduler` repository an
 | Scorer           | Description                                | Env Vars |
 |------------------|--------------------------------------------|----------|
 | Session-aware    | Prefers pods from same session             | `ENABLE_SESSION_AWARE_SCORER`, `SESSION_AWARE_SCORER_WEIGHT`, `PREFILL_ENABLE_SESSION_AWARE_SCORER`, `PREFILL_SESSION_AWARE_SCORER_WEIGHT` |
-| Prefix-aware     | Matches prompt prefix                      | `ENABLE_PREFIX_AWARE_SCORER`, `PREFIX_AWARE_SCORER_WEIGHT`, `PREFILL_ENABLE_PREFIX_AWARE_SCORER`, `PREFILL_PREFIX_AWARE_SCORER_WEIGHT`, `PREFIX_SCORER_BLOCK_SIZE`, `PREFIX_SCORER_CACHE_CAPACITY`, `PREFIX_SCORER_MAX_BLOCK_CACHE_SIZE`|
+| Prefix-aware     | Matches prompt prefix                      | `ENABLE_PREFIX_AWARE_SCORER`, `PREFIX_AWARE_SCORER_WEIGHT`, `PREFILL_ENABLE_PREFIX_AWARE_SCORER`, `PREFILL_PREFIX_AWARE_SCORER_WEIGHT`, `PREFIX_SCORER_CACHE_CAPACITY`, `PREFIX_SCORER_CACHE_BLOCK_SIZE`|
 | KVCache-aware    | Optimizes for KV reuse                     | `ENABLE_KVCACHE_AWARE_SCORER`, `KVCACHE_INDEXER_REDIS_ADDR`, `PREFILL_ENABLE_KVCACHE_AWARE_SCORER`, `PREFILL_KVCACHE_INDEXER_REDIS_ADDR`, `HF_TOKEN`, `KVCACHE_INDEXER_REDIS_ADDR` |
 | Load-aware       | Avoids busy pods                           | `ENABLE_LOAD_AWARE_SCORER`, `LOAD_AWARE_SCORER_WEIGHT`, `PREFILL_ENABLE_LOAD_AWARE_SCORER`, `PREFILL_LOAD_AWARE_SCORER_WEIGHT` |
 
@@ -92,6 +92,11 @@ In case Disaggrigated Prefill is enabled, you should also define the following e
 - Toggle P/D mode: `PD_ENABLED=true`
 - Threshold: `PD_PROMPT_LEN_THRESHOLD=<value>`
 
+### Prefix Aware Scorer Configuration
+
+- `PREFIX_SCORER_CACHE_CAPACITY` - the cache capacity sets the maximum number of blocks the LRU cache can store. A block maps from a chunk of a prompt to a set of pods that are estimated to have the prefix of the prompt that ends at the keyed chunk.
+- `PREFIX_SCORER_CACHE_BLOCK_SIZE` - the cache block size defines the length of the prompt chunk that a block is keyed by.
+
 #### Prefill Scorers:
 ```bash
 export PREFILL_ENABLE_SESSION_AWARE_SCORER=true