1 files changed, 35 insertions, 18 deletions
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index f26019c72e..745f09f523 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -119,25 +119,16 @@ If you want to cache a fragment under certain conditions, you can use
 
 The `render` helper can also cache individual templates rendered for a collection.
 It can even one up the previous example with `each` by reading all cache
-templates at once instead of one by one. This is done automatically if the template
-rendered by the collection includes a `cache` call. Take a collection that renders
-a `products/_product.html.erb` partial for each element:
-
-```ruby
-render products
-```
-
-If `products/_product.html.erb` starts with a `cache` call like so:
+templates at once instead of one by one. This is done by passing `cached: true` when rendering the collection:
 
 ```html+erb
-<% cache product do %>
-  <%= product.name %>
-<% end %>
+<%= render partial: 'products/product', collection: @products, cached: true %>
 ```
 
-All the cached templates from previous renders will be fetched at once with much
-greater speed. There's more info on how to make your templates [eligible for
-collection caching](http://api.rubyonrails.org/classes/ActionView/Template/Handlers/ERB.html#method-i-resource_cache_call_pattern).
+All cached templates from previous renders will be fetched at once with much
+greater speed. Additionally, the templates that haven't yet been cached will be
+written to cache and multi fetched on the next render.
+
 
 ### Russian Doll Caching
 
@@ -521,12 +512,38 @@ class ProductsController < ApplicationController
 end
 ```
 
-### A note on weak ETags
+### Strong v/s Weak ETags
+
+Rails generates weak ETags by default. Weak ETags allow semantically equivalent
+responses to have the same ETags, even if their bodies do not match exactly.
+This is useful when we don't want the page to be regenerated for minor changes in
+response body.
+
+Weak ETags have a leading `W/` to differentiate them from strong ETags.
+
+```
+  W/"618bbc92e2d35ea1945008b42799b0e7" → Weak ETag
+  "618bbc92e2d35ea1945008b42799b0e7" → Strong ETag
+```
+
+Unlike weak ETag, strong ETag implies that response should be exactly the same
+and byte by byte identical. Useful when doing Range requests within a
+large video or PDF file. Some CDNs support only strong ETags, like Akamai.
+If you absolutely need to generate a strong ETag, it can be done as follows.
+
+```ruby
+  class ProductsController < ApplicationController
+    def show
+      @product = Product.find(params[:id])
+      fresh_when last_modified: @product.published_at.utc, strong_etag: @product
+    end
+  end
+```
 
-Etags generated by Rails are weak by default. Weak etags allow symantically equivalent responses to have the same etags, even if their bodies do not match exactly. This is useful when we don't want the page to be regenerated for minor changes in response body. If you absolutely need to generate a strong etag, it can be assigned to the header directly.
+You can also set the strong ETag directly on the response.
 
 ```ruby
-  response.add_header "ETag", Digest::MD5.hexdigest(response.body)
+  response.strong_etag = response.body # => "618bbc92e2d35ea1945008b42799b0e7"
 ```
 
 References