diff --git a/NEWS.md b/NEWS.md
index c9fb1de9..33743cee 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -2,7 +2,7 @@
 
 **Deprecation warning**: Next major release will drop support for `Node.js 6 LTS`, `npm 3.x` and `yarn`. You'll be able to use the latest ES features as soon as we release 7.0.0. In the meantime, as a developer, you should keep compatibility with Node.js 6 LTS and keep updated both `package-lock.json` and `yarn.lock` files.
 
-## 6.5.2
+## 6.6.0
 Released 2018-mm-dd
 
 Announcements:
@@ -14,7 +14,8 @@ Announcements:
 - Update dev deps:
   - jshint@2.9.7
   - mocha@5.2.0
-
+- Be able to customize max waiting workers parameter
+- Handle max number of waiting workers error as `429 Too many requests` error.
 
 ## 6.5.1
 Released 2018-12-26
diff --git a/config/environments/development.js.example b/config/environments/development.js.example
index be15ca6c..0cddec6c 100644
--- a/config/environments/development.js.example
+++ b/config/environments/development.js.example
@@ -139,6 +139,10 @@ var config = {
           // Important: check the configuration of uv_threadpool_size to use suitable value
           poolSize: 8,
 
+          // The maximum number of waiting clients of the pool of internal mapnik backend
+          // This maximum number is per mapnik renderer created in Windshaft's RendererFactory
+          poolMaxWaitingClients: 64,
+
           // Whether grainstore will use a child process or not to transform CartoCSS into Mapnik XML.
           // This will prevent blocking the main thread.
           useCartocssWorkers: false,
diff --git a/config/environments/production.js.example b/config/environments/production.js.example
index c058e27f..f73a095c 100644
--- a/config/environments/production.js.example
+++ b/config/environments/production.js.example
@@ -139,6 +139,10 @@ var config = {
           // Important: check the configuration of uv_threadpool_size to use suitable value
           poolSize: 8,
 
+          // The maximum number of waiting clients of the pool of internal mapnik backend
+          // This maximum number is per mapnik renderer created in Windshaft's RendererFactory
+          poolMaxWaitingClients: 64,
+
           // Whether grainstore will use a child process or not to transform CartoCSS into Mapnik XML.
           // This will prevent blocking the main thread.
           useCartocssWorkers: false,
diff --git a/config/environments/staging.js.example b/config/environments/staging.js.example
index 8d89e43f..9bef903d 100644
--- a/config/environments/staging.js.example
+++ b/config/environments/staging.js.example
@@ -139,6 +139,10 @@ var config = {
           // Important: check the configuration of uv_threadpool_size to use suitable value
           poolSize: 8,
 
+          // The maximum number of waiting clients of the pool of internal mapnik backend
+          // This maximum number is per mapnik renderer created in Windshaft's RendererFactory
+          poolMaxWaitingClients: 64,
+
           // Whether grainstore will use a child process or not to transform CartoCSS into Mapnik XML.
           // This will prevent blocking the main thread.
           useCartocssWorkers: false,
diff --git a/config/environments/test.js.example b/config/environments/test.js.example
index 184675a7..7f4e4149 100644
--- a/config/environments/test.js.example
+++ b/config/environments/test.js.example
@@ -139,6 +139,10 @@ var config = {
           // Important: check the configuration of uv_threadpool_size to use suitable value
           poolSize: 8,
 
+          // The maximum number of waiting clients of the pool of internal mapnik backend
+          // This maximum number is per mapnik renderer created in Windshaft's RendererFactory
+          poolMaxWaitingClients: 64,
+
           // Whether grainstore will use a child process or not to transform CartoCSS into Mapnik XML.
           // This will prevent blocking the main thread.
           useCartocssWorkers: false,
diff --git a/lib/cartodb/server_options.js b/lib/cartodb/server_options.js
index 5c19ee9a..5c9da8c6 100644
--- a/lib/cartodb/server_options.js
+++ b/lib/cartodb/server_options.js
@@ -9,6 +9,7 @@ var rendererConfig = _.defaults(global.environment.renderer || {}, {
     statsInterval: 60000,
     mapnik: {
         poolSize: 8,
+        poolMaxWaitingClients: 64,
         metatile: 2,
         bufferSize: 64,
         snapToGrid: false,