diff --git a/src/library/cache.cr b/src/library/cache.cr
index d0d3f01..686ae1f 100644
--- a/src/library/cache.cr
+++ b/src/library/cache.cr
@@ -1,6 +1,7 @@
 require "digest"
 
 require "./entry"
+require "./title"
 require "./types"
 
 # Base class for an entry in the LRU cache.
@@ -81,6 +82,31 @@ class SortedEntriesCacheEntry < CacheEntry(Array(String), Array(Entry))
   end
 end
 
+class SortedTitlesCacheEntry < CacheEntry(Array(String), Array(Title))
+  def self.to_save_t(value : Array(Title))
+    value.map &.id
+  end
+
+  def self.to_return_t(value : Array(String))
+    value.map { |title_id| Library.default.title_hash[title_id].not_nil! }
+  end
+
+  def instance_size
+    instance_sizeof(SortedTitlesCacheEntry) +   # sizeof itself
+      instance_sizeof(String) + @key.bytesize + # allocated memory for @key
+      @value.size * (instance_sizeof(String) + sizeof(String)) +
+      @value.sum(&.bytesize) # elements in Array(String)
+  end
+
+  def self.gen_key(username : String, titles : Array(Title), opt : SortOptions?)
+    titles_sig = Digest::SHA1.hexdigest (titles.map &.id).to_s
+    user_context = opt && opt.method == SortMethod::Progress ? username : ""
+    sig = Digest::SHA1.hexdigest (titles_sig + user_context +
+                                  (opt ? opt.to_tuple.to_s : "nil"))
+    "#{sig}:sorted_titles"
+  end
+end
+
 class String
   def instance_size
     instance_sizeof(String) + bytesize
@@ -101,14 +127,17 @@ struct Tuple(*T)
   end
 end
 
-alias CacheableType = Array(Entry) | String | Tuple(String, Int32)
+alias CacheableType = Array(Entry) | Array(Title) | String | Tuple(String, Int32)
 alias CacheEntryType = SortedEntriesCacheEntry |
+                       SortedTitlesCacheEntry |
                        CacheEntry(String, String) |
                        CacheEntry(Tuple(String, Int32), Tuple(String, Int32))
 
 def generate_cache_entry(key : String, value : CacheableType)
   if value.is_a? Array(Entry)
     SortedEntriesCacheEntry.new key, value
+  elsif value.is_a? Array(Title)
+    SortedTitlesCacheEntry.new key, value
   else
     CacheEntry(typeof(value), typeof(value)).new key, value
   end
diff --git a/src/library/entry.cr b/src/library/entry.cr
index ec11cb1..4c9c96f 100644
--- a/src/library/entry.cr
+++ b/src/library/entry.cr
@@ -89,13 +89,7 @@ class Entry
       @sort_title = sort_title
     end
 
-    [false, true].each do |ascend|
-      [SortMethod::Auto, SortMethod::Title].each do |sort_method|
-        sorted_entries_cache_key = SortedEntriesCacheEntry.gen_key @book.id,
-          username, @book.entries, SortOptions.new(sort_method, ascend)
-        LRUCache.invalidate sorted_entries_cache_key
-      end
-    end
+    @book.remove_sorted_caches [SortMethod::Auto, SortMethod::Title], username
   end
 
   def sort_title_db
@@ -213,11 +207,7 @@ class Entry
     @book.parents.each do |parent|
       LRUCache.invalidate "#{parent.id}:#{username}:progress_sum"
     end
-    [false, true].each do |ascend|
-      sorted_entries_cache_key = SortedEntriesCacheEntry.gen_key @book.id,
-        username, @book.entries, SortOptions.new(SortMethod::Progress, ascend)
-      LRUCache.invalidate sorted_entries_cache_key
-    end
+    @book.remove_sorted_caches [SortMethod::Progress], username
 
     TitleInfo.new @book.dir do |info|
       if info.progress[username]?.nil?
diff --git a/src/library/title.cr b/src/library/title.cr
index 9eacf4e..f61f01d 100644
--- a/src/library/title.cr
+++ b/src/library/title.cr
@@ -317,14 +317,7 @@ class Title
       @sort_title = sort_title
     end
 
-    [false, true].each do |ascend|
-      [SortMethod::Auto, SortMethod::Title].each do |sort_method|
-        sorted_entries_cache_key =
-          SortedEntriesCacheEntry.gen_key @id, username, @entries,
-            SortOptions.new(sort_method, ascend)
-        LRUCache.invalidate sorted_entries_cache_key
-      end
-    end
+    remove_sorted_caches [SortMethod::Auto, SortMethod::Title], username
   end
 
   def sort_title_db
@@ -605,17 +598,32 @@ class Title
     zip + titles.flat_map &.deep_entries_with_date_added
   end
 
+  def remove_sorted_caches(sort_methods : Array(SortMethod), username : String)
+    [false, true].each do |ascend|
+      sort_methods.each do |sort_method|
+        sorted_entries_cache_key =
+          SortedEntriesCacheEntry.gen_key @id, username, @entries,
+            SortOptions.new(sort_method, ascend)
+        LRUCache.invalidate sorted_entries_cache_key
+      end
+    end
+    parents.each do |parent|
+      [false, true].each do |ascend|
+        sort_methods.each do |sort_method|
+          sorted_titles_cache_key = SortedTitlesCacheEntry.gen_key username,
+            parent.titles, SortOptions.new(sort_method, ascend)
+          LRUCache.invalidate sorted_titles_cache_key
+        end
+      end
+    end
+  end
+
   def bulk_progress(action, ids : Array(String), username)
     LRUCache.invalidate "#{@id}:#{username}:progress_sum"
     parents.each do |parent|
       LRUCache.invalidate "#{parent.id}:#{username}:progress_sum"
     end
-    [false, true].each do |ascend|
-      sorted_entries_cache_key =
-        SortedEntriesCacheEntry.gen_key @id, username, @entries,
-          SortOptions.new(SortMethod::Progress, ascend)
-      LRUCache.invalidate sorted_entries_cache_key
-    end
+    remove_sorted_caches [SortMethod::Progress], username
 
     selected_entries = ids
       .map { |id|
diff --git a/src/util/util.cr b/src/util/util.cr
index 2814c6c..74738b7 100644
--- a/src/util/util.cr
+++ b/src/util/util.cr
@@ -86,7 +86,11 @@ def env_is_true?(key : String) : Bool
   val.downcase.in? "1", "true"
 end
 
-def sort_titles(titles : Array(Title), opt : SortOptions, username : String)
+def sort_titles(titles : Array(Title), opt : SortOptions, username : String) : Array(Title)
+  cache_key = SortedTitlesCacheEntry.gen_key username, titles, opt
+  cached_titles = LRUCache.get cache_key
+  return cached_titles if cached_titles.is_a? Array(Title)
+
   ary = titles
 
   case opt.method
@@ -110,6 +114,7 @@ def sort_titles(titles : Array(Title), opt : SortOptions, username : String)
 
   ary.reverse! unless opt.not_nil!.ascend
 
+  LRUCache.set generate_cache_entry cache_key, ary
   ary
 end