diff --git a/app/controllers/autocomplete_controller.rb b/app/controllers/autocomplete_controller.rb
index 68c46d793..0b36168db 100644
--- a/app/controllers/autocomplete_controller.rb
+++ b/app/controllers/autocomplete_controller.rb
@@ -8,6 +8,10 @@ class AutocompleteController < ApplicationController
     @autocomplete = AutocompleteService.new(@query, @type, current_user: CurrentUser.user, limit: @limit)
 
     @results = @autocomplete.autocomplete_results
+    @expires_in = @autocomplete.cache_duration
+    @public = @autocomplete.cache_publicly?
+
+    expires_in @expires_in, public: @public unless response.cache_control.present?
     respond_with(@results)
   end
 end
diff --git a/app/logical/autocomplete_service.rb b/app/logical/autocomplete_service.rb
index d05cb6696..8ae91392d 100644
--- a/app/logical/autocomplete_service.rb
+++ b/app/logical/autocomplete_service.rb
@@ -1,4 +1,6 @@
 class AutocompleteService
+  extend Memoist
+
   POST_STATUSES = %w[active deleted pending flagged appealed banned modqueue unmoderated]
 
   STATIC_METATAGS = {
@@ -197,4 +199,29 @@ class AutocompleteService
     results = autocomplete_tag(string).map { |result| result[:value] }
     [query, results]
   end
+
+  def cache_duration
+    if autocomplete_results.size == limit
+      24.hours
+    else
+      1.hour
+    end
+  end
+
+  # Queries that don't depend on the current user are safe to cache publicly.
+  def cache_publicly?
+    if type == :tag_query && parsed_search&.type == :tag
+      true
+    elsif type.in?(%i[tag artist wiki_page pool opensearch])
+      true
+    else
+      false
+    end
+  end
+
+  def parsed_search
+    PostQueryBuilder.new(query).terms.first
+  end
+
+  memoize :autocomplete_results
 end