diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 4881f2ac15..b88f1a3ac8 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2400,10 +2400,10 @@ By default, `LUCENE`.
 
 [[index.threads]]index.threads::
 +
-Number of threads to use for indexing in normal interactive operations. If set
-to 0, indexing will be done in the same thread as the interactive operation.
+Number of threads to use for indexing in normal interactive operations.
 +
-Defaults to 0 if not set, or set to a negative value.
+If not set or set to a negative value, defaults to 1 plus half of the number of
+logical CPUs as returned by the JVM.
 
 [[index.batchThreads]]index.batchThreads::
 +
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/index/IndexModule.java b/gerrit-server/src/main/java/com/google/gerrit/server/index/IndexModule.java
index befd5ed7e0..a3d3ad5dd9 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/index/IndexModule.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/index/IndexModule.java
@@ -140,7 +140,7 @@ public class IndexModule extends LifecycleModule {
       threads = config.getInt("index", null, "threads", 0);
     }
     if (threads <= 0) {
-      return MoreExecutors.newDirectExecutorService();
+      threads = Runtime.getRuntime().availableProcessors() / 2 + 1;
     }
     return MoreExecutors.listeningDecorator(
         workQueue.createQueue(threads, "Index-Interactive"));