Don't make me wait! or Building High-Performance Web Applications

1. “Don’t make me wait” or Building High-Performance Web Apps Stoyan Stefanov, Yahoo! Brownbag at eBay August 11, 2009

2. About me •  Yahoo! Search •  Yahoo! Exceptional Performance •  YSlow 2.0 architect •  http://smush.it •  Books, articles •  http://phpied.com

3. Importance of performance •  Is it dev? QA? Afterthought? •  Developers love it •  But is it good for business?

4. Importance of performance •  Self-regulating system •  Slow down = lose users •  We all hate slow pages

5. Importance of performance 1sec = -2.8% revenue

6. Importance of performance Gets worse with time After-effect

7. Importance of performance •  Yahoo!: 400 ms slower = 5-9% drop in full-page traffic

8. Importance of performance Slower pages get less traffic

9. Importance of performance From 4-6 seconds to 1.5 seconds

10. “The premature optimization… •  … is the root of all evil” Knuth •  “Make it right before you make it fast” Crockford

11. Measure, measure, measure •  measure •  profile •  monitor

12. On trade-offs “…everything has its drawbacks, as the man said when his mother-in-law died, and they came upon him for the funeral expenses” Jerome K. Jerome Three man in a boat

13. The Life of Page 2.0 HTML page request onload settles request sent marriage? R.I.P. conception birth graduation User perceived “onload” happens somewhere here

14. The waterfall

15. The Waterfall 1.  Less stuff 2.  Smaller stuff 3.  Out of the way 4.  Start early

17. Less HTTP requests •  Combine components

18. Less HTTP requests •  Before: <script src="jquery.js"></script> <script src="jquery.twitter.js"></script> <script src="jquery.cookie.js"></script> <script src="myapp.js"></script>

19. Less HTTP requests •  After: <script src="all.js" type="text/javascript"> </script>

20. Less HTTP requests •  Saved 3 HTTP requests

21. Less HTTP requests •  repeat for CSS: <link href="all.css" rel="stylesheet" type="text/css” />

22. Less HTTP requests •  CSS sprites for background images background‐position: ‐22px ‐0px; width: 12px; height: 10px;

23. Less HTTP requests CSS sprites •  Before: 15 requests, 6.8 K •  After: 1 request, 1.4 K

24. Less HTTP requests •  CSS sprites – a pain, but there are tools http://csssprites.com http://spritegen.website‐performance.org/

25. Less HTTP requests •  Inline images with data: scheme

26. Less HTTP requests •  data: URI scheme $ php ‐r "echo base64_encode(file_get_contents('my.png'));” iVBORw0KGgoAAAANSUhEUgAAAAQAAAADCAIAAAA7ljmRAAAAGElEQVQIW2P4 DwcMDAxAfBvMAhEQMYgcACEHG8ELxtbPAAAAAElFTkSuQmCC

27. Less HTTP requests •  data: URI scheme background‐image: url("data:image/png;base64,iVBORw0KG...");

28. Less HTTP requests •  data: URI scheme <img src="data:image/png;base64,iVBOR..." />

29. Less HTTP requests •  data: URI scheme •  works in IE!...

30. Less HTTP requests •  data: URI scheme •  works in IE8!

31. Less HTTP requests •  data: URI scheme •  MHTML for IE < 8 http://www.phpied.com/mhtml-when-you-need-data-uris-in-ie7-and-under/ http://www.hedgerwow.com/360/dhtml/base64-image/demo.php

32. Less HTTP requests - drawback •  atomic components •  invalidated by small changes •  need to schedule changes

33. Less stuff? Cache •  Cache is less universal than we think •  You can help http://yuiblog.com/blog/2007/01/04/performance-research-part-2/

34. “never expire” policy •  Static components with far- future Expires header •  JS, CSS, img ExpiresActive On ExpiresByType image/png "access plus 10 years"

35. Inline vs. external •  a.k.a. less http vs. more cache •  how about both?

36. Inline vs. external •  First visit: 1. Inline 2. Lazy-load the external file 3. Write a cookie

37. Inline vs. external •  Later visits: 1. Read cookie 2. Refer to the external file

38. Less stuff – duh! •  No 404s •  No duplicates •  No near-duplicates

39. Duplicates •  2903384828078080_1.jpg •  2204648665418080_1.jpg •  3801476378448080_1.jpg •  3801476377438080_1.jpg

40. Near duplicates •  30x30 vs. 49x49 •  Rounded corners, shadows

41. The Waterfall 1.  Less stuff ✔ 2.  Smaller stuff 3.  Out of the way 4.  Start early

43. Gzip

44. Gzip •  What to gzip? HTML, XHTML, XML, W00TChaMaCallitML, CSS, JS, JSON, HTC, plain text… all but binary • (btw, check those older SWFs too)

45. Gzip •  How to gzip? AddOutputFilterByType DEFLATE text/html text/… Header append Vary Accept‐Encoding http://www.sitepoint.com/article/web‐site‐optimization‐steps

46. Minify •  Before /** * The dom module provides helper methods for * manipulating Dom elements. * @module dom * */ (function() { var Y = YAHOO.util, // internal shorthand getStyle, // for load time browser branching setStyle, // ditto propertyCache = {}, // for faster hyphen converts reClassNameCache = {}, // cache regexes for className document = window.document; // cache for faster lookups YAHOO.env._id_counter = YAHOO.env._id_counter || 0;

47. Minify •  After (function(){var B=YAHOO.util,K,I,J={},F={},M=window.document;YAHOO.env._id_counter=YAHOO.en v._id_counter||0;

48. Minify •  YUI Compressor •  Minifies JS and CSS •  Tolerates * and _ hacks •  More than minification

49. Minify •  Minify inline code too

50. Gzip or minification? •  62,885 bytes - original jQuery (back in Aug 2007) •  31,822 - minified with the YUI Compressor •  19,758 - original gzipped •  10,818 - minified and gzipped FTW http://www.julienlecomte.net/blog/2007/08/13/

51. Minify •  minify HTML? •  dangerous •  write minified HTML echo '<div class="my">', '<p>', $db‐>get('name'), '</p>', '<div>';

52. Minify •  Strip quotes? No closing tags? •  Some sites do <body bgcolor=#ffffff text=#000000 link=#0000cc vlink=#551a8b alink=#ff0000 onload="...." topmargin=3 marginheight=3><textarea id=csi style=display:none>

53. Minify •  Relative URLs

54. Relative URLs on my blog >>> document.links.length 204 >>> … loop … indexOf(‘http://www.phpied.com’) 130 >>> ‘http://www.phpied.com’.length 21 >>> 21*130/1024 2.666015625

55. Relative URLs on my blog •  Compare: •  2.66K - absolute links •  1.4K - sprite of 15 elements

56. Images •  http://smush.it

57. Images Loss- 1.  No GIFs, PNG8 less 2.  Crush PNGs 3.  run JPEGs through jpegtran 4.  Gifsicle for animations http://yuiblog.com/blog/2008/11/14/imageopt-3/

58. Images – progressive JPEG •  for images ~10K+

59. Images •  eBay homepage could save 20% image sizes •  Search –> 10%+ •  Item -> 30% (50K+)

60. Images – duh! 1.  Don’t scale in HTML 2.  Generated images should be crushed PNGs too

61. Images •  It’s only human to forget •  All you need is a process so you don’t have to remember

62. 204 •  The world’s smallest component? •  204 No Content <?php header("HTTP/1.0 204 No Content"); // .... do your job, e.g. logging ?> http://www.phpied.com/204-no-content/

63. The Waterfall 1.  Less stuff ✔ 2.  Smaller stuff ✔ 3.  Out of the way 4.  Start early

65. Free-falling waterfalls •  Less DNS lookups – fetch components from not more than 2-4 domains •  Less redirects •  Blocking JavaScript/CSS

66. Not free-falling

67. JavaScript rocks! •  But also blocks html js png png

68. Non-blocking JavaScript •  Include via DOM html js png png var js = document.createElement('script'); js.src = 'myscript.js'; var h = document.getElementsByTagName('head')[0]; h.appendChild(js);

69. Non-blocking JavaScript •  And what about my inline scripts? •  Setup a collection (registry) of inline scripts

70. Step 1 •  Inline in the <head>: var myapp = { stuff: [], };

71. Step 2 •  Add to the registry Instead of: <script>alert('boo!');</script> Do: <script> myapp.stuff.push(function(){ alert('boo!'); }); </script>

72. Step 3 •  Execute all var l = myapp.stuff.length; for(var i = 0, i < l; i++) { myapp.stuff[i](); }

73. Blocking CSS? But they do block: •  In FF2 •  When followed by an inline script

74. The Waterfall 1.  Less stuff ✔ 2.  Smaller stuff ✔ 3.  Out of the way ✔ 4.  Start early

76. Cookies •  less cookies •  no cookies •  www vs. non-www 3000 bytes of cookies cost 78ms

77. flush() early html png js  css html js png ✔ css

78. flush() <html> <head> <script src="my.js" type="text/javascript"></script> <link href="my.css" type="text/css" rel="stylesheet" /> </head> <?php flush() ?> <body> ....

79. Chunked encoding HTTP/1.1 200 OK Content‐Type: text/plain Transfer‐Encoding: chunked 25 This is the data in the first chunk 1C and this is the second one 0

80. Chunked encoding •  Progressive rendering - Semantic app chunks vs. - Server-level chunks

81. Progressive rendering Chunk #1 Chunk #2 Chunk #3

82. Progressive rendering •  Server-level flush: bing.com – every 1 or 2K google (ungzip) – every 4K

83. Progressive + source order 1 3 2 4

84. The Waterfall 1.  Less stuff ✔ 2.  Smaller stuff ✔ 3.  Out of the way ✔ 4.  Start early ✔

85. ✓ Waterfall

86. Life after onload

87. Life after onload 1.  Lazy-load 2.  Pre-load 3.  XHR 4.  JavaScript optimizations 5.  Rendering

88. Lazy-load •  bells & whistles •  badges & widgets

89. Preload •  to help next page’s waterfall •  img, CSS, JS, DNS lookups

90. XHR (Ajax) •  small – gzip, JSON •  less – Expires •  GET over POST

91. GET vs. POST for XHR var url = 'test.php'; var request = new XMLHttpRequest(); request.open("POST", url, false); // … request.send('test=1');

92. GET vs. POST for XHR

93. JavaScript optimizations •  Number of DOM elements •  DOM access •  Event delegation

94. Touching the DOM function foo() { for (var count = 0; count < 1000; count++) { document.body.innerHTML += 1; } }

95. Touching the DOM function foo() { var inner = ''; for (var count = 0; count < 1000; count++) { inner += 1; } document.body.innerHTML += inner; 1000 } times faster

96. Rendering •  CSS on top •  No separate print CSS •  CSS refactoring •  No AlphaImageLoader •  Expensive elements •  No CSS expressions •  Image dimensions

97. CSS early on •  No separate print CSS file /* screen styles */ #nav {...} .banner {...} /* print styles */ @media print { #nav {display: none} .banner {display: none;} }

98. CSS refactoring •  CSS tends to grow •  Find unused selectors – DustMeSelectors extension •  Cleanup things like: #header #menu {...} div#menu {...} ul li {...}

99. No AlphaImageLoader #some‐element { background: url(image.png); _background: none; _filter:progid:DXImageTransform.Microsoft.AlphaImageLoader (src='image.png', sizingMethod='crop'); } http://yuiblog.com/blog/2008/12/08/imageopt-5/

100. Expensive elements •  Avoid or limit <applet> <object> (IE) <iframe>

101. Life after onload 1.  Lazy-load ✔ 2.  Pre-load ✔ 3.  XHR ✔ 4.  JavaScript optimizations ✔ 5.  Rendering ✔

102. ✓ Life after onload

103. YSlow 2.0

104. YSlow •  Firebug extension •  Why (is my page) slow? http://developer.yahoo.com/yslow/

105. Yahoo! performance rules 1.  Make Fewer HTTP Requests 19.  Reduce the Number of DOM Elements 2.  Use a Content Delivery Network 20.  Split Components Across Domains 3.  Add an Expires or a Cache-Control 21.  Minimize the Number of iframes Header 22.  No 404s 4.  Gzip Components 23.  Reduce Cookie Size 5.  Put Stylesheets at the Top 24.  Use Cookie-free Domains for 6.  Put Scripts at the Bottom Components 7.  Avoid CSS Expressions 25.  Minimize DOM Access 8.  Make JavaScript and CSS External 26.  Develop Smart Event Handlers 9.  Reduce DNS Lookups 27.  Choose <link> over @import 10.  Minify JavaScript and CSS 28.  Avoid Filters 11.  Avoid Redirects 29.  Optimize Images 12.  Remove Duplicate JS and CSS 30.  Optimize CSS Sprites 13.  Configure ETags 31.  Don't Scale Images in HTML 14.  Make Ajax Cacheable 32.  Make favicon.ico Small and 15.  Flush the Buffer Early Cacheable 16.  Use GET for AJAX Requests 33.  Keep Components under 25K 17.  Post-load Components 34.  Pack Components into a Multipart Document 18.  Preload Components

106. YSlow 1.0. rules 1.  Make Fewer HTTP Requests 19.  Reduce the Number of DOM Elements 2.  Use a Content Delivery Network 20.  Split Components Across Domains 3.  Add an Expires or a Cache-Control 21.  Minimize the Number of iframes Header 22.  No 404s 4.  Gzip Components 23.  Reduce Cookie Size 5.  Put Stylesheets at the Top 24.  Use Cookie-free Domains for 6.  Put Scripts at the Bottom Components 7.  Avoid CSS Expressions 25.  Minimize DOM Access 8.  Make JavaScript and CSS External 26.  Develop Smart Event Handlers 9.  Reduce DNS Lookups 27.  Choose <link> over @import 10.  Minify JavaScript and CSS 28.  Avoid Filters 11.  Avoid Redirects 29.  Optimize Images 12.  Remove Duplicate JS and CSS 30.  Optimize CSS Sprites 13.  Configure ETags 31.  Don't Scale Images in HTML 14.  Make Ajax Cacheable 32.  Make favicon.ico Small and 15.  Flush the Buffer Early Cacheable 16.  Use GET for AJAX Requests 33.  Keep Components under 25K 17.  Post-load Components 34.  Pack Components into a Multipart Document 18.  Preload Components

107. YSlow 2.0. rules 1.  Make Fewer HTTP Requests 19.  Reduce the Number of DOM Elements 2.  Use a Content Delivery Network 20.  Split Components Across Domains 3.  Add an Expires or a Cache-Control 21.  Minimize the Number of iframes Header 22.  No 404s 4.  Gzip Components 23.  Reduce Cookie Size 5.  Put Stylesheets at the Top 24.  Use Cookie-free Domains for 6.  Put Scripts at the Bottom Components 7.  Avoid CSS Expressions 25.  Minimize DOM Access 8.  Make JavaScript and CSS External 26.  Develop Smart Event Handlers 9.  Reduce DNS Lookups 27.  Choose <link> over @import 10.  Minify JavaScript and CSS 28.  Avoid Filters 11.  Avoid Redirects 29.  Optimize Images 12.  Remove Duplicate JS and CSS 30.  Optimize CSS Sprites 13.  Configure ETags 31.  Don't Scale Images in HTML 14.  Make Ajax Cacheable 32.  Make favicon.ico Small and 15.  Flush the Buffer Early Cacheable 16.  Use GET for AJAX Requests 33.  Keep Components under 25K 17.  Post-load Components 34.  Pack Components into a Multipart Document 18.  Preload Components

108. YSlow 1.0. rule weights 1.  Make Fewer HTTP Requests 8 2.  Use a Content Delivery Network 6 3.  Add an Expires or a Cache-Control Header 10 4.  Gzip Components 8 5.  Put Stylesheets at the Top 4 6.  Put Scripts at the Bottom 4 7.  Avoid CSS Expressions 3 8.  Make JavaScript and CSS External 4 9.  Reduce DNS Lookups 3 10.  Minify JavaScript 4 11.  Avoid Redirects 4 12.  Remove Duplicate JS 4 13.  Configure Etags 2

109. YSlow 2.0. rule weights 1.  Make Fewer HTTP Requests 8 2.  Use a Content Delivery Network 6 3.  Add an Expires or a Cache-Control Header 10 4.  Gzip Components 8 5.  Put Stylesheets at the Top 4 6.  Put Scripts at the Bottom 4 7.  Avoid CSS Expressions 3 8.  Make JavaScript and CSS External 4 9.  Reduce DNS Lookups 3 10.  Minify JavaScript and CSS 4 11.  Avoid Redirects 4 12.  Remove Duplicate JS and CSS 4 13.  Configure Etags 2 14.  Make Ajax Cacheable 4 16.  Use GET for AJAX Requests 3 19.  Reduce the Number of DOM Elements 3 22.  No 404s 4 23.  Reduce Cookie Size 3 24.  Use Cookie-free Domains for Components 3 28.  Avoid Filters 4 31.  Don't Scale Images in HTML 3 32.  Make favicon.ico Small and Cacheable 2

110. YSlow score foreach rule total += rule score * rule weight end foreach score = total / sum of rule weights

111. YSlow letter score •  (A) 90 – 100 •  (B) 80 – 89 •  (C) 70 – 79 •  (D) 60 – 69 •  (E) 50 – 59 •  (F) under 50

112. Custom rule 1.  Add an Expires Header 2.  Configure Etags Rule Weight Rule score * Expires header 10 100 (A) 1000 ETags 2 50 (E) 100 Total 12 1100 Score = 1100 / 12 = 91.66 (A) Note: max weight is 10, min rule score is 0

113. Rule scores •  Start from 100 •  Penalty for every offence

114. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External # ok -points 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS JS 3 -4/off 11.  Avoid Redirects CSS 2 -4/off 12.  Remove Duplicate JS and CSS 13.  Configure Etags img 6 -3/off 14.  Make Ajax Cacheable 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

115. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects -10 points 12.  Remove Duplicate JS and CSS 13.  Configure Etags per 14.  Make Ajax Cacheable offending 16.  Use GET for AJAX Requests component 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

116. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add Expires Headers 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS If expiration 11.  Avoid Redirects is less than 12.  Remove Duplicate JS and CSS 13.  Configure Etags 2 days 14.  Make Ajax Cacheable subtract -11 16.  Use GET for AJAX Requests points per 19.  Reduce the Number of DOM Elements component 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

117. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS -11 points 11.  Avoid Redirects per 12.  Remove Duplicate JS and CSS 13.  Configure Etags offending 14.  Make Ajax Cacheable component 16.  Use GET for AJAX Requests bigger than 19.  Reduce the Number of DOM Elements 500 bytes 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

120. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS -2 points 13.  Configure Etags per Make Ajax Cacheable 14.  16.  Use GET for AJAX Requests expression 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

121. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JS and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags 14.  Make Ajax Cacheable Score is 16.  Use GET for AJAX Requests always n/a 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

122. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 4 domains 12.  Remove Duplicate JS and CSS ok 13.  Configure Etags -5 points Make Ajax Cacheable 14.  16.  Use GET for AJAX Requests per domain 19.  Reduce the Number of DOM Elements otherwise 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

123. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify -10 points 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS per 13.  Configure Etags offender, Make Ajax Cacheable 14.  16.  Use GET for AJAX Requests including 19.  Reduce the Number of DOM Elements inline 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

124. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags -10 points 14.  Make Ajax Cacheable per redirect 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

125. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  No Duplicates -5 points per 13.  Configure Etags 14.  Make Ajax Cacheable duplicate 16.  Use GET for AJAX Requests JS or CSS 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

126. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS -11 points 13.  Configure ETags per 14.  Make Ajax Cacheable offending 16.  Use GET for AJAX Requests component 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

127. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom -5 points 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External per XHR 9.  Reduce DNS Lookups without at 10.  Minify JavaScript and CSS least 1 hour 11.  Avoid Redirects expiration 12.  Remove Duplicate JS and CSS 13.  Configure Etags 14.  Make Ajax Cacheable 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

128. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top -5 points 6.  Put Scripts at the Bottom per 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External non-GET 9.  Reduce DNS Lookups XHR 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags 14.  Make Ajax Cacheable 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

129. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top -10 points 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions for every 8.  Make JavaScript and CSS External 250 9.  Reduce DNS Lookups elements 10.  Minify JavaScript and CSS over 900 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags 14.  Make Ajax Cacheable 16.  Use GET for AJAX Requests 19.  Reduce # of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

130. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags -5 points 14.  Make Ajax Cacheable per 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements offending component 22.  No 404s 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

131. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects -10 points 12.  Remove Duplicate JS and CSS per 13.  Configure Etags 14.  Make Ajax Cacheable component 16.  Use GET for AJAX Requests requested 19.  Reduce the Number of DOM Elements with over No 404s 22.  1000 bytes 23.  Reduce Cookie Size of cookies 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

132. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions -5 points 8.  Make JavaScript and CSS External per Reduce DNS Lookups 9.  10.  Minify JavaScript and CSS component 11.  Avoid Redirects requested 12.  Remove Duplicate JS and CSS with a 13.  Configure Etags cookie 14.  Make Ajax Cacheable 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements 22.  No 404s 23.  Reduce Cookie Size 24.  Cookie-free Domains 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

133. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS -5 points 13.  Configure Etags 14.  Make Ajax Cacheable per offense 16.  Use GET for AJAX Requests or 19.  Reduce the Number of DOM Elements -2 if using No 404s 22.  23.  Reduce Cookie Size _filter hack 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

134. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS 13.  Configure Etags -5 points 14.  Make Ajax Cacheable per scaled 16.  Use GET for AJAX Requests 19.  Reduce the Number of DOM Elements down 22.  No 404s image 23.  Reduce Cookie Size 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Make favicon.ico Small and Cacheable

135. Rule penalties 1.  Make Fewer HTTP Requests 2.  Use a Content Delivery Network 3.  Add an Expires or a Cache-Control Header 4.  Gzip Components 5.  Put Stylesheets at the Top 6.  Put Scripts at the Bottom 7.  Avoid CSS Expressions 8.  Make JavaScript and CSS External 9.  Reduce DNS Lookups 10.  Minify JavaScript and CSS 11.  Avoid Redirects 12.  Remove Duplicate JS and CSS -5 points if 13.  Configure Etags 14.  Make Ajax Cacheable size is over 16.  Use GET for AJAX Requests 2000 bytes 19.  Reduce the Number of DOM Elements and -5 if no No 404s 22.  23.  Reduce Cookie Size expiration 24.  Use Cookie-free Domains for Components 28.  Avoid Filters 31.  Don't Scale Images in HTML 32.  Small cacheable favicon

136. ✓ YSlow 2.0

137. Words of Wisdom

138. Performance matters •  It affects the user happiness •  It affects the bottom line

139. Front-end •  That’s where most of the time is spent

140. It’s a marathon •  Not a sprint •  Measure, monitor, link to business metrics •  Bugs are expensive as the time passes, performance bugs even more so

141. What’s a low-hanging fruit? •  Takes one engineer •  Takes 15 minutes Steve Krug

142. For non-low-hanging fruits? 1.  Pick 2 or 3 2.  Fix, measure one by one 3.  Come back and iterate

143. Thank you! Stoyan Stefanov @stoyanstefanov http://www.phpied.com