diff --git a/dropbox/provider/unstructured.py b/dropbox/provider/unstructured.py
index 186582089..3b7bf6ca7 100644
--- a/dropbox/provider/unstructured.py
+++ b/dropbox/provider/unstructured.py
@@ -1,12 +1,15 @@
+import sys
 import asyncio
 import aiohttp
 import logging
+import functools
 from collections import OrderedDict
 from flask import current_app as app
 
 logger = logging.getLogger(__name__)
 
-CACHE_SIZE = 256
+CACHE_LIMIT_BYTES = 20 * 1024 * 1024  # 20 MB to bytes
+TIMEOUT_SECONDS = 20
 
 unstructured = None
 
@@ -14,19 +17,29 @@
 class UnstructuredRequestSession:
     def __init__(self, unstructured_base_url, api_key):
         self.get_content_url = f"{unstructured_base_url}/general/v0/general"
-        self.headers = {"unstructured-api-key": api_key}
+        self.api_key = api_key
         # Manually cache because functools.lru_cache does not support async methods
         self.cache = OrderedDict()
         self.start_session()
 
     def start_session(self):
         self.loop = asyncio.new_event_loop()
-        self.session = aiohttp.ClientSession(loop=self.loop)
+        # Create ClientTimeout object to apply timeout for every request in the session
+        client_timeout = aiohttp.ClientTimeout(total=TIMEOUT_SECONDS)
+        self.session = aiohttp.ClientSession(loop=self.loop, timeout=client_timeout)
 
     def close_loop(self):
         self.loop.stop()
         self.loop.close()
 
+    def cache_size(self):
+        # Calculate the total size of values in bytes
+        total_size_bytes = functools.reduce(
+            lambda a, b: a + b, map(lambda v: sys.getsizeof(v), self.cache.values()), 0
+        )
+
+        return total_size_bytes
+
     def cache_get(self, key):
         self.cache.move_to_end(key)
 
@@ -35,7 +48,7 @@ def cache_get(self, key):
     def cache_put(self, key, item):
         self.cache[key] = item
 
-        if len(self.cache) > CACHE_SIZE:
+        while self.cache_size() > CACHE_LIMIT_BYTES:
             self.cache.popitem()
 
     async def close_session(self):
@@ -53,9 +66,12 @@ async def get_unstructured_content(self, file):
         data = aiohttp.FormData()
         data.add_field("files", file_data, filename=file_name)
 
+        # API key optional if self-hosted
+        headers = {} if self.api_key is None else {"unstructured-api-key": self.api_key}
+
         async with self.session.post(
             self.get_content_url,
-            headers=self.headers,
+            headers=headers,
             data=data,
         ) as response:
             content = await response.json()
@@ -91,13 +107,10 @@ def get_unstructured_client():
     if unstructured is not None:
         return unstructured
 
-    # Fetch environment variables
     assert (
         unstructured_base_url := app.config.get("UNSTRUCTURED_BASE_URL")
     ), "DROPBOX_UNSTRUCTURED_BASE_URL must be set"
-    assert (
-        api_key := app.config.get("UNSTRUCTURED_API_KEY")
-    ), "DROPBOX_UNSTRUCTURED_API_KEY must be set"
+    api_key = app.config.get("UNSTRUCTURED_API_KEY", None)
 
     unstructured = UnstructuredRequestSession(unstructured_base_url, api_key)