diff --git a/blocking.py b/blocking.py
index 206682efc..53346c136 100644
--- a/blocking.py
+++ b/blocking.py
@@ -9,6 +9,7 @@ __module_group__ = "ActivityPub"
 
 import os
 import json
+import time
 from datetime import datetime
 from utils import isAccountDir
 from utils import getCachedPostFilename
@@ -167,7 +168,32 @@ def getDomainBlocklist(baseDir: str) -> str:
     return blockedStr
 
 
-def isBlockedDomain(baseDir: str, domain: str) -> bool:
+def updateBlockedCache(baseDir: str,
+                       blockedCache: [],
+                       blockedCacheLastUpdated: int,
+                       blockedCacheUpdateSecs: int) -> int:
+    """Updates the cache of globally blocked domains held in memory
+    """
+    currTime = int(time.time())
+    if blockedCacheLastUpdated > currTime:
+        print('WARN: Cache updated in the future')
+        blockedCacheLastUpdated = 0
+    secondsSinceLastUpdate = currTime - blockedCacheLastUpdated
+    if secondsSinceLastUpdate < blockedCacheUpdateSecs:
+        return blockedCacheLastUpdated
+    globalBlockingFilename = baseDir + '/accounts/blocking.txt'
+    if not os.path.isfile(globalBlockingFilename):
+        return blockedCacheLastUpdated
+    with open(globalBlockingFilename, 'r') as fpBlocked:
+        blockedLines = fpBlocked.readlines()
+        blockedCache.clear()
+        for line in blockedLines:
+            blockedCache.append(line.replace('\n', ''))
+    return currTime
+
+
+def isBlockedDomain(baseDir: str, domain: str,
+                    blockedCache: [] = None) -> bool:
     """Is the given domain blocked?
     """
     if '.' not in domain:
@@ -186,16 +212,24 @@ def isBlockedDomain(baseDir: str, domain: str) -> bool:
 
     allowFilename = baseDir + '/accounts/allowedinstances.txt'
     if not os.path.isfile(allowFilename):
-        # instance block list
-        globalBlockingFilename = baseDir + '/accounts/blocking.txt'
-        if os.path.isfile(globalBlockingFilename):
-            with open(globalBlockingFilename, 'r') as fpBlocked:
-                blockedStr = fpBlocked.read()
+        if blockedCache:
+            for blockedStr in blockedCache:
                 if '*@' + domain in blockedStr:
                     return True
                 if shortDomain:
                     if '*@' + shortDomain in blockedStr:
                         return True
+        else:
+            # instance block list
+            globalBlockingFilename = baseDir + '/accounts/blocking.txt'
+            if os.path.isfile(globalBlockingFilename):
+                with open(globalBlockingFilename, 'r') as fpBlocked:
+                    blockedStr = fpBlocked.read()
+                    if '*@' + domain in blockedStr:
+                        return True
+                    if shortDomain:
+                        if '*@' + shortDomain in blockedStr:
+                            return True
     else:
         # instance allow list
         if not shortDomain:
diff --git a/daemon.py b/daemon.py
index 955bebeee..b53021918 100644
--- a/daemon.py
+++ b/daemon.py
@@ -114,6 +114,7 @@ from media import attachMedia
 from media import pathIsImage
 from media import pathIsVideo
 from media import pathIsAudio
+from blocking import updateBlockedCache
 from blocking import mutePost
 from blocking import unmutePost
 from blocking import setBrochMode
@@ -487,7 +488,14 @@ class PubServer(BaseHTTPRequestHandler):
         # is the User-Agent domain blocked
         blockedUA = False
         if not agentDomain.startswith(callingDomain):
-            blockedUA = isBlockedDomain(self.server.baseDir, agentDomain)
+            self.server.blockedCacheLastUpdated = \
+                updateBlockedCache(self.server.baseDir,
+                                   self.server.blockedCache,
+                                   self.server.blockedCacheLastUpdated,
+                                   self.server.blockedCacheUpdateSecs)
+
+            blockedUA = isBlockedDomain(self.server.baseDir, agentDomain,
+                                        self.server.blockedCache)
             # if self.server.debug:
             if blockedUA:
                 print('Blocked User agent: ' + agentDomain)
@@ -1212,7 +1220,15 @@ class PubServer(BaseHTTPRequestHandler):
 
         messageDomain, messagePort = \
             getDomainFromActor(messageJson['actor'])
-        if isBlockedDomain(self.server.baseDir, messageDomain):
+
+        self.server.blockedCacheLastUpdated = \
+            updateBlockedCache(self.server.baseDir,
+                               self.server.blockedCache,
+                               self.server.blockedCacheLastUpdated,
+                               self.server.blockedCacheUpdateSecs)
+
+        if isBlockedDomain(self.server.baseDir, messageDomain,
+                           self.server.blockedCache):
             print('POST from blocked domain ' + messageDomain)
             self._400()
             self.server.POSTbusy = False
@@ -15180,6 +15196,16 @@ def runDaemon(userAgentsBlocked: [],
     # contains threads used to send posts to followers
     httpd.followersThreads = []
 
+    # create a cache of blocked domains in memory.
+    # This limits the amount of slow disk reads which need to be done
+    httpd.blockedCache = []
+    httpd.blockedCacheLastUpdated = 0
+    httpd.blockedCacheUpdateSecs = 120
+    httpd.blockedCacheLastUpdated = \
+        updateBlockedCache(baseDir, httpd.blockedCache,
+                           httpd.blockedCacheLastUpdated,
+                           httpd.blockedCacheUpdateSecs)
+
     # cache to store css files
     httpd.cssCache = {}
 
diff --git a/utils.py b/utils.py
index ad277004b..fd159e8af 100644
--- a/utils.py
+++ b/utils.py
@@ -1441,7 +1441,9 @@ def _isReservedName(nickname: str) -> bool:
                      'shares', 'fonts', 'icons', 'avatars',
                      'welcome', 'helpimages',
                      'bookmark', 'bookmarks', 'tlbookmarks',
-                     'ignores')
+                     'ignores', 'linksmobile', 'newswiremobile',
+                     'minimal', 'search', 'eventdelete',
+                     'searchemoji')
     if nickname in reservedNames:
         return True
     return False