This document discusses techniques for improving web performance. It begins by explaining that websites that have many similar pages, like e-commerce sites, need to care about performance to avoid lower conversions and higher bounce rates. It then discusses metrics for perceived performance, with pages feeling sluggish over 100ms and users' attention typically dropping off after 1 second. The document provides examples of caching strategies in Rails like fragment caching at the row and table levels to improve performance. It also discusses leveraging the database instead of calculating values in the view. Other techniques mentioned include pre-heating caches during off-hours, leveraging HTTP caching with ETags, and using server-side caching to serve static files without application involvement.

1. WebPerformance
Why and How
Stefan Wintermeyer (@wintermeyer)

2. Two Hearts in
One Chest

3. What websites do not
have to care about
WebPerformance?

4. next-weeks-lottery-numbers.com
If you run the only page with this information!

5. What websites DO
have to care about
WebPerformance?

6. last-weeks-lottery-numbers.com
Because there are a lot of similar pages.

7. What's the impact of slow sites?
Lower conversions and engagement, higher bounce rates...
Ilya Grigorik @igrigorik
Make The Web Faster, Google

8. Yo ho ho and a few billion pages of RUM
How speed affects bounce rate
@igrigorik

9. Usability Engineering 101
Delay User reaction
0 - 100 ms Instant
100 - 300 ms Feels sluggish
300 - 1000 ms Machine is working...
1 s+ Mental context switch
10 s+ I'll come back later...
Stay under 250
ms to feel "fast".
Stay under 1000
ms to keep users
attention.
@igrigorik

10. Web Search Delay
Experiment
Type of Delay Delay (ms)
Duration
(weeks)
Impact on Avg.
Daily Searches
Pre-header 100 4 -0.20 %
Pre-header 200 6 -0.59%
Post-header 400 6 0.59%
Post-ads 200 4 0.30%
Source: https://www.igvita.com/slides/2012/webperf-crash-course.pdf

11. For many, mobile is the one and only internet
device!
Country Mobile-only users
Egypt 70%
India 59%
South Africa 57%
Indonesia 44%
United States 25%
onDevice Research
@igrigorik

12. < 1.000 ms Page Loading Time on
3G ist der Mount Everest.

13. The (short) life of our 1000 ms budget
3G (200 ms
RTT)
4G(80 ms RTT)
Control plane (200-2500 ms) (50-100 ms)
DNS lookup 200 ms 80 ms
TCP Connection 200 ms 80 ms
TLS handshake (200-400 ms) (80-160 ms)
HTTP request 200 ms 80 ms
Leftover budget 0-400 ms 500-760 ms
Network overhead
of one HTTP
request!
@igrigorik

14. Some WebPerf Problems
can’t be fixed within Phoenix.
If your page initially loads 3
MB of JavaScript it will never
be fast.

15. Webpage Rendering
Basics

16. Network
HTML
DOM
CSS
CSSOM JavaScript
Render tree
Layout
Paint

17. Network
HTML
DOM
CSS
CSSOM JavaScript
Render tree
Layout
Paint

18. Network
HTML
DOM
CSS
CSSOM JavaScript
Render tree
Layout
Paint

19. Network
HTML
DOM
CSS
CSSOM JavaScript
Render tree
Layout
Paint

20. Network
HTML
DOM
CSS
CSSOM JavaScript
Render tree
Layout
Paint

21. This rendering process
takes a minimum of 100 ms
which we have to subtract
from the 1,000 ms.

22. Download a file with
HTTP 1.1 over TCP

23. Latency
clientZeit
0 ms
80 ms
160 ms
240 ms
320 ms
10 TCP Segmente (14.600 Bytes)
20 TCP Segmente (29.200 Bytes)
40 TCP Segmente (15.592 Bytes)
server
SYN
ACK
ACK
GET
SYN,ACK
ACK
ACK

24. TCP Slow-Start
KB
0
55
110
165
220
Roundtrip
1. 2. 3. 4.
214KB
100KB
43KB
14KB
114KB
57KB
29KB
14KB

25. HTTP 2 you can parallel
download multiple files over
the same TCP connection.
Plus better header compression. Plus push, …
More on that later.

26. Waterfall
www.webpagetest.org
https://rubyconference.by

27. 3G Run => https://www.webpagetest.org/result/
180412_BK_4b5755e7d0717d0f218a88edf5a691a9/

31. LTE Run => https://www.webpagetest.org/result/
180412_6W_0697a100d965b385b53917b77d51d081/

34. LTE run => https://www.webpagetest.org/result/
180316_5B_de436fb724593d7b746b9c1f89ff3c2d/

38. Can I interest you in a
Rails caching example?
It’s so much better in Phoenixland but we can learn from it.

39. Example Online Shop

40. $ rails new shop
$ cd shop
$ rails g scaffold Category name
$ rails g scaffold Product category:references
name description
price:decimal{8,2}
$ rails g scaffold User email first_name
last_name password_digest
$ rails g scaffold Review user:references
product:references
rating:integer
$ rails db:migrate

41. Shop domain model
Category
name string
Product
description text
name string
price decimal (8,2)
Review
rating integer
User
email string
first_name string
last_name string
password_digest string

42. app/models/product.rb:
class Product < ApplicationRecord
belongs_to :category
has_many :reviews
def number_of_stars
if reviews.any?
reviews.average(:rating).round
else
nil
end
end
end

43. db/seeds.rb:
Category.create(name: "A")
Category.create(name: "B")
Category.create(name: "C")
100.times do
Product.create(name: Faker::Food.dish,
description: Faker::Food.description,
category: Category.all.sample,
price: rand(20))
end
50.times do
user = User.create(first_name: Faker::Name.first_name,
last_name: Faker::Name.last_name)
products = Product.all
3.times do
Review.create(user: user,
product: products.sample,
rating: rand(5))
end
end

44. app/views/products/index.html.erb:
<table class="table table-striped">
[…]
<tbody>
<% @products.each do |product| %>
<tr>
<td><%= product.category.name %></td>
<td><%= product.name %></td>
<td><%= product.description %></td>
<td><%= number_to_currency(product.price) %></td>
<td>
<% product.number_of_stars.to_i.times do %>
<img src="<%= asset_path( 'star.svg' ) %>“ />
<% end %>
</td>
[…]
</tr>
<% end %>
</tbody>
</table>

46. Completed 200 OK in
497ms (Views: 460.4ms |
ActiveRecord: 34.1ms)
Development env.

47. The (short) life of our 1000 ms budget
3G (200 ms
RTT)
4G(80 ms RTT)
Control plane (200-2500 ms) (50-100 ms)
DNS lookup 200 ms 80 ms
TCP Connection 200 ms 80 ms
TLS handshake (200-400 ms) (80-160 ms)
HTTP request 200 ms 80 ms
Leftover budget 0-400 ms 500-760 ms
Network overhead
of one HTTP
request!
@igrigorik
497ms
And we don’t have product images yet.

48. Development environment?
Are you crazy?!
Hold your horses!
I’ll switch to production
environment later.

49. Fragment Caching

50. $ rails dev:cache
Development mode is now being cached.
By default caching is disabled in dev env.

51. 1. Step
Single Row

54. app/views/products/index.html.erb:
<tbody>
<% @products.each do |product| %>
<% cache product do %>
<tr>
<td><%= product.category.name %></td>
<td><%= product.name %></td>
<td><%= product.description %></td>
<td><%= number_to_currency(product.price) %></td>
<td>
<% product.number_of_stars.to_i.times do %>
<img src="<%= asset_path( 'star.svg' ) %>" />
<% end %>
</td>
[...]
</tr>
<% end %>
<% end %>
</tbody>

55. app/views/products/index.html.erb:
<tbody>
<% @products.each do |product| %>
<% cache product do %>
<tr>
<td><%= product.category.name %></td>
<td><%= product.name %></td>
<td><%= product.description %></td>
<td><%= number_to_currency(product.price) %></td>
<td>
<% product.number_of_stars.to_i.times do %>
<img src="<%= asset_path( 'star.svg' ) %>" />
<% end %>
</td>
[...]
</tr>
<% end %>
<% end %>
</tbody>

56. app/models/review.rb:
class Review < ApplicationRecord
belongs_to :user
belongs_to :product, touch: true
end
Product
description text
name string
price decimal (8,2)
Review
rating integer
User
email string
first_name string
last_name string
password_digest string

57. Total Views Activerecord
Vanilla 497ms 460 ms 34 ms
Fragment Cache Row 79 ms 74,6 ms 1 ms

58. 2. Step
The Complete Table
=> Russian Doll

61. app/views/products/index.html.erb:
<tbody>
<% cache @products do %>
<% @products.each do |product| %>
<% cache product do %>
<tr>
<td><%= product.category.name %></td>
<td><%= product.name %></td>
<td><%= product.description %></td>
<td><%= number_to_currency(product.price) %></td>
<td>
<% product.number_of_stars.to_i.times do %>
<img src="<%= asset_path( 'star.svg' ) %>" />
<% end %>
</td>
[…]
</tr>
<% end %>
<% end %>
<% end %>
</tbody>

62. app/views/products/index.html.erb:
<tbody>
<% cache @products do %>
<% @products.each do |product| %>
<% cache product do %>
<tr>
<td><%= product.category.name %></td>
<td><%= product.name %></td>
<td><%= product.description %></td>
<td><%= number_to_currency(product.price) %></td>
<td>
<% product.number_of_stars.to_i.times do %>
<img src="<%= asset_path( 'star.svg' ) %>" />
<% end %>
</td>
[…]
</tr>
<% end %>
<% end %>
<% end %>
</tbody>

63. Total Views Activerecord
Vanilla 497ms 460 ms 34 ms
Fragment Cache Row 79 ms 74,6 ms 1 ms
Fragment Cache Table 53 ms 49,5 ms 0,6 ms

64. Use the Database!

65. app/models/product.rb:
class Product < ApplicationRecord
belongs_to :category
has_many :reviews
def number_of_stars
if reviews.any?
reviews.average(:rating).round
else
nil
end
end
end

66. app/models/product.rb:
class Product < ApplicationRecord
belongs_to :category
has_many :reviews
end
$ rails g migration AddNumberOfStarsToProduct
number_of_stars:integer
$ rails db:migrate

67. app/models/product.rb:
class Review < ApplicationRecord
belongs_to :user
belongs_to :product, touch: true
after_create :recalculate_product_rating
after_destroy :recalculate_product_rating
private
def recalculate_product_rating
rating = product.reviews.average(:rating).round
if rating != self.product.number_of_stars
product.update_attribute(:number_of_stars, rating)
end
end
end

68. Total Views Activerecord
Vanilla 497ms 460 ms 34 ms
Fragment Cache Row 79 ms 74,6 ms 1 ms
Fragment Cache Table 53 ms 49,5 ms 0,6 ms
Plus Database Improvents 40 ms 39 ms 0,5 ms
Production Env. 35 ms 34 ms 0,5 ms

69. Warning:
Fragment Caching is
slower the 1st request!
Why? Rails checks if the Fragment Cache exists.
When it doesn’t it renders the view and writes the cache
which is time consuming.

70. Need More Speed?
You are at the right place! ;-)
Have a look at http://phoenixframework.org
Phoenix takes 5 ms for the same page.
BTW: without caching

71. HTTP Caching

72. Web browsers and proxies
don‘t want to fetch identical
resources multiple times.

73. The idea of Etags and
Last-Modified

74. Web browser:
„My user wants to fetch xyz.html.
I cached a copy last week.
Is that still good?“

75. Web server:
„xyz.html hasn‘t changed since
last week.
Go a head with your copy!“
aka 304 Not Modified

76. > curl -I http://0.0.0.0:3000/products
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
X-Ua-Compatible: IE=Edge
Etag: "9a779b80e4b0ac3c60d29807e302deb7"
[...]
> curl -I http://0.0.0.0:3000/products
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
X-Ua-Compatible: IE=Edge
Etag: "fa8fc1e981833a6885b583d351c4d823"

77. > curl -I http://0.0.0.0:3000/products
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
X-Ua-Compatible: IE=Edge
Etag: "9a779b80e4b0ac3c60d29807e302deb7"
[...]
> curl -I http://0.0.0.0:3000/products
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
X-Ua-Compatible: IE=Edge
Etag: "fa8fc1e981833a6885b583d351c4d823"

78. Set the Etag
class ProductsController <
ApplicationController
# GET /products
def index
@products = Product.all
fresh_when :etag => @products
end
[...]

79. > curl -I http://0.0.0.0:3000/products -c
cookies.txt
HTTP/1.1 200 OK
Etag: "4d348810e69400799e2ab684c0ef4777"
> curl -I http://0.0.0.0:3000/products -b
cookies.txt
HTTP/1.1 200 OK
Etag: "4d348810e69400799e2ab684c0ef4777"
The cookie is needed for the CSRF-Token.

80. > curl -I http://0.0.0.0:3000/products -b
cookies.txt --header 'If-None-Match:
"4d348810e69400799e2ab684c0ef4777"'
HTTP/1.1 304 Not Modified
Etag: "4d348810e69400799e2ab684c0ef4777"
304!

81. Win-Win of a 304
• The Browser doesn’t have to
download everything.
• The Server doesn’t have to
render the view which is the
most time consuming bit.

82. Not good enough?

83. Writing the initial cache
wastes a lot of time.

84. Let‘s preheat the cache
in off business hours!
Cron is your friend.

85. Use the night to
preheat your cache.
And don‘t be afraid
of brute force!

86. A U T O B A H N

87. The fastest page is
delivered by Nginx
without ever contacting
Phoenix or Ruby on Rails.

88. ├── Gemfile
├── [...]
├── public
│ ├── 404.html
│ ├── 422.html
│ ├── 500.html
│ ├── favicon.ico
│ └── robots.txt
├── [...]
That‘s already
done for the
files in the
public directory.

89. Add caches_page to your
controller to save views as static
gz files in your public directory:
caches_page :index, :show,
:gzip => :true
Add gem actionpack-page_caching for Rails 5.2

90. Brute Force is your friend!
During the night the server has a
hard time to stay awake any way.

91. Tricky part:
How to delete out of date
gz files?

92. after_update :expire_cache
before_destroy :expire_cache
private
def expire_cache
ActionController::Base.expire_page(Rails.application.routes.url_h
elpers.company_path(self))
ActionController::Base.expire_page(Rails.application.routes.url_h
elpers.companies_path)
end
app/models/product.rb

93. caches_page
vs.
!current_user.nil?
???

94. caches_page is good to cache
customized user content too.
It just takes more thinking.

95. Let us assume a user base
of 10,000,000 people.

96. /tmp ᐅ wget http://www.railsconf.com/2013/talks
--2013-04-27 21:04:24-- http://www.railsconf.com/2013/talks
Resolving www.railsconf.com... 107.20.162.205
Connecting to www.railsconf.com|107.20.162.205|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: ‘talks’
[ <=> ] 74,321 258KB/
s in 0.3s
2013-04-27 21:04:25 (258 KB/s) - ‘talks’ saved [74321]
/tmp ᐅ du -hs talks
76K talks
/tmp ᐅ gzip talks
/tmp ᐅ du -hs talks.gz
28K talks.gz
/tmp ᐅ

97. /tmp ᐅ du -hs talks.gz
28K talks.gz
28K * 10,000,000 = 0,26 TB

98. 28K * 10,000,000 = 0,26 TB
Harddrive space is cheap.
By saving the files non-gz and using
a data deduplication file system you
just need 5-10% of the 0,26 TB.
Nginx can gzip the files on the fly.

99. Nginx will happily read a
cookie and find the pre-
rendered page in a given
directory structure.

100. HTTP/1.1 vs. HTTP/2

101. HTTP/2 provides an average
WebPerformance improvement
of 20%.
It’s a no-brainer.
You have to use it!

102. CDNs, HTTP/2 and Rails 5.2

103. Long story short:
In most cases where a CDN made
sense with HTTP/1.1 it doesn’t
make sense any more.
Just deliver everything from your
Rails server!

104. Image Formats
It is still an often underused way of saving bandwidth.

105. JPEG, PNG or WebP

106. https://caniuse.com/#feat=webp

107. CSS

108. Less CSS = Faster Webpages
Do not underestimate the WebPerformance impact of
optimized CSS.

109. Webfonts

110. If possible don’t use
Webfonts.

111. Apache vs. Nginx

112. It doesn’t matter!
Just use your favorite
one.

113. Brotli vs. gzip

114. Always offer both!
Brotli can be used to
save bandwidth and
CPU-Resources.

115. Heroku vs. Bare Metal

116. Heroku is good for a quick start
but has never been a good choice
for good WebPerformance. Bare
Metal is the way to go if you need
maximum WebPerformance.
BTW: It’s cheaper too.

117. P R E L O A D I N G U N D
P R E F E T C H I N G

118. P R E L O A D I N G U N D P R E F E T C H I N G
<link rel="dns-prefetch"...
<link rel="prefetch"...
DNS pre-resolution
TCP pre-connect
prefresh
preloader

119. M A N U A L D N S - P R E F E T C H
<link rel="dns-prefetch" href="//abc.com">
http://www.chromium.org/developers/design-documents/dns-prefetching
„Most common names like google.com and yahoo.com are resolved so
often that most local ISP's name resolvers can answer in closer to 80-120ms.
If the domain name in question is an uncommon name, then a query may
have to go through numerous resolvers up and down the hierarchy, and the
delay can average closer to 200-300ms.“

120. P R E F E T C H
<link rel="prefetch" href=„http://abc.com/important.js">
http://www.whatwg.org/specs/web-apps/current-work/#link-type-prefetch
„The prefetch keyword indicates that preemptively fetching and caching the
specified resource is likely to be beneficial, as it is highly likely that the user
will require this resource.“
T I P P : " A C C E P T - R A N G E S : B Y T E S “ H E A D E R

121. Y O U C A N T E L L N G I N X T O
P U S H T H O S E F I L E S V I A H T T P / 2 .

122. The Most
Important Tool?

123. Set a Time Budget!
If you run out of your time budget you have to
cancel features on your website.

124. Is WebPerformance really so hard?

125. The WebPerf Bible. => https://hpbn.co

126. @wintermeyer

127. sw@wintermeyer-consulting.de
last name | twitter | github
e-mail