diff --git a/_sidebar.md b/_sidebar.md
index 6ef2da8..e27c1bd 100644
--- a/_sidebar.md
+++ b/_sidebar.md
@@ -8,8 +8,10 @@
 - [Ruby](categories/ruby.md)
 - [Interview](categories/interviews/interview.md)
 - [Software Design](categories/software-design.md)
-- [Queues](categories/queues.md)
-    - [Kafka](categories/queues/kafka.md)
+- [Apps and Tools](categories/apps.md)
+    - [Kafka](categories/apps/kafka.md)
+    - [MQTT](categories/apps/mqtt.md)
+    - [Elasticsearch](categories/apps/elasticsearch.md)
 - [Database](categories/database.md)
 - [Application](categories/application.md)
 - [Web Scraping](categories/web-scraping.md)
diff --git a/categories/apps.md b/categories/apps.md
new file mode 100644
index 0000000..6f1b53a
--- /dev/null
+++ b/categories/apps.md
@@ -0,0 +1 @@
+# Some apps and tools
diff --git a/categories/apps/elasticsearch.md b/categories/apps/elasticsearch.md
new file mode 100644
index 0000000..546f20c
--- /dev/null
+++ b/categories/apps/elasticsearch.md
@@ -0,0 +1,3 @@
+# Elasticsearch
+
+Elasticsearch is a search engine based on the Lucene library. It provides a distributed, multitenant-capable full-text search engine with an HTTP web interface and schema-free JSON documents.
diff --git a/categories/queues/kafka.md b/categories/apps/kafka.md
similarity index 100%
rename from categories/queues/kafka.md
rename to categories/apps/kafka.md
diff --git a/categories/queues.md b/categories/apps/mqtt.md
similarity index 77%
rename from categories/queues.md
rename to categories/apps/mqtt.md
index 448b571..693a9e9 100644
--- a/categories/queues.md
+++ b/categories/apps/mqtt.md
@@ -1,11 +1,3 @@
-# Message Queue
-
-## Rabbitmq
-
-## activeMQ
-
-## Redis
-
 ## MQTT
 
 A lightweight messaging protocol for small sensors and mobile devices, optimized for high-latency or unreliable networks. It's basically a machine-to-machine `protocol`