Fix broken links (donnemartin#204)

README.md

@@ -602,7 +602,7 @@ Sites with heavy traffic work well with pull CDNs, as traffic is spread out more
 
 ### Source(s) and further reading
 
-* [Globally distributed content delivery](http://repository.cmu.edu/cgi/viewcontent.cgi?article=2112&context=compsci)
+* [Globally distributed content delivery](https://figshare.com/articles/Globally_distributed_content_delivery/6605972)
 * [The differences between push and pull CDNs](http://www.travelblogadvice.com/technical/the-differences-between-push-and-pull-cdns/)
 * [Wikipedia](https://en.wikipedia.org/wiki/Content_delivery_network)
 
@@ -1092,7 +1092,7 @@ Databases often benefit from a uniform distribution of reads and writes across i
 
 ### Client caching
 
-Caches can be located on the client side (OS or browser), [server side](#reverse-proxy), or in a distinct cache layer.
+Caches can be located on the client side (OS or browser), [server side](#reverse-proxy-web-server), or in a distinct cache layer.
 
 ### CDN caching
 
@@ -1363,7 +1363,7 @@ TCP is a connection-oriented protocol over an [IP network](https://en.wikipedia.
 
 If the sender does not receive a correct response, it will resend the packets.  If there are multiple timeouts, the connection is dropped.  TCP also implements [flow control](https://en.wikipedia.org/wiki/Flow_control_(data)) and [congestion control](https://en.wikipedia.org/wiki/Network_congestion#Congestion_control).  These guarantees cause delays and generally result in less efficient transmission than UDP.
 
-To ensure high throughput, web servers can keep a large number of TCP connections open, resulting in high memory usage.  It can be expensive to have a large number of open connections between web server threads and say, a [memcached](#memcached) server.  [Connection pooling](https://en.wikipedia.org/wiki/Connection_pool) can help in addition to switching to UDP where applicable.
+To ensure high throughput, web servers can keep a large number of TCP connections open, resulting in high memory usage.  It can be expensive to have a large number of open connections between web server threads and say, a [memcached](https://memcached.org/) server.  [Connection pooling](https://en.wikipedia.org/wiki/Connection_pool) can help in addition to switching to UDP where applicable.
 
 TCP is useful for applications that require high reliability but are less time critical.  Some examples include web servers, database info, SMTP, FTP, and SSH.
 
@@ -1605,18 +1605,18 @@ Handy metrics based on numbers above:
 | Design Google docs | [code.google.com](https://code.google.com/p/google-mobwrite/)<br/>[neil.fraser.name](https://neil.fraser.name/writing/sync/) |
 | Design a key-value store like Redis | [slideshare.net](http://www.slideshare.net/dvirsky/introduction-to-redis) |
 | Design a cache system like Memcached | [slideshare.net](http://www.slideshare.net/oemebamo/introduction-to-memcached) |
-| Design a recommendation system like Amazon's | [hulu.com](http://tech.hulu.com/blog/2011/09/19/recommendation-system.html)<br/>[ijcai13.org](http://ijcai13.org/files/tutorial_slides/td3.pdf) |
+| Design a recommendation system like Amazon's | [hulu.com](https://web.archive.org/web/20170406065247/http://tech.hulu.com/blog/2011/09/19/recommendation-system.html)<br/>[ijcai13.org](http://ijcai13.org/files/tutorial_slides/td3.pdf) |
 | Design a tinyurl system like Bitly | [n00tc0d3r.blogspot.com](http://n00tc0d3r.blogspot.com/) |
 | Design a chat app like WhatsApp | [highscalability.com](http://highscalability.com/blog/2014/2/26/the-whatsapp-architecture-facebook-bought-for-19-billion.html)
 | Design a picture sharing system like Instagram | [highscalability.com](http://highscalability.com/flickr-architecture)<br/>[highscalability.com](http://highscalability.com/blog/2011/12/6/instagram-architecture-14-million-users-terabytes-of-photos.html) |
 | Design the Facebook news feed function | [quora.com](http://www.quora.com/What-are-best-practices-for-building-something-like-a-News-Feed)<br/>[quora.com](http://www.quora.com/Activity-Streams/What-are-the-scaling-issues-to-keep-in-mind-while-developing-a-social-network-feed)<br/>[slideshare.net](http://www.slideshare.net/danmckinley/etsy-activity-feeds-architecture) |
 | Design the Facebook timeline function | [facebook.com](https://www.facebook.com/note.php?note_id=10150468255628920)<br/>[highscalability.com](http://highscalability.com/blog/2012/1/23/facebook-timeline-brought-to-you-by-the-power-of-denormaliza.html) |
 | Design the Facebook chat function | [erlang-factory.com](http://www.erlang-factory.com/upload/presentations/31/EugeneLetuchy-ErlangatFacebook.pdf)<br/>[facebook.com](https://www.facebook.com/note.php?note_id=14218138919&id=9445547199&index=0) |
 | Design a graph search function like Facebook's | [facebook.com](https://www.facebook.com/notes/facebook-engineering/under-the-hood-building-out-the-infrastructure-for-graph-search/10151347573598920)<br/>[facebook.com](https://www.facebook.com/notes/facebook-engineering/under-the-hood-indexing-and-ranking-in-graph-search/10151361720763920)<br/>[facebook.com](https://www.facebook.com/notes/facebook-engineering/under-the-hood-the-natural-language-interface-of-graph-search/10151432733048920) |
-| Design a content delivery network like CloudFlare | [cmu.edu](http://repository.cmu.edu/cgi/viewcontent.cgi?article=2112&context=compsci) |
+| Design a content delivery network like CloudFlare | [figshare.com](https://figshare.com/articles/Globally_distributed_content_delivery/6605972) |
 | Design a trending topic system like Twitter's | [michael-noll.com](http://www.michael-noll.com/blog/2013/01/18/implementing-real-time-trending-topics-in-storm/)<br/>[snikolov .wordpress.com](http://snikolov.wordpress.com/2012/11/14/early-detection-of-twitter-trends/) |
 | Design a random ID generation system | [blog.twitter.com](https://blog.twitter.com/2010/announcing-snowflake)<br/>[github.com](https://github.com/twitter/snowflake/) |
-| Return the top k requests during a time interval | [ucsb.edu](https://icmi.cs.ucsb.edu/research/tech_reports/reports/2005-23.pdf)<br/>[wpi.edu](http://davis.wpi.edu/xmdv/docs/EDBT11-diyang.pdf) |
+| Return the top k requests during a time interval | [cs.ucsb.edu](https://www.cs.ucsb.edu/sites/cs.ucsb.edu/files/docs/reports/2005-23.pdf)<br/>[wpi.edu](http://davis.wpi.edu/xmdv/docs/EDBT11-diyang.pdf) |
 | Design a system that serves data from multiple data centers | [highscalability.com](http://highscalability.com/blog/2009/8/24/how-google-serves-data-from-multiple-datacenters.html) |
 | Design an online multiplayer card game | [indieflashblog.com](http://www.indieflashblog.com/how-to-create-an-asynchronous-multiplayer-game.html)<br/>[buildnewgames.com](http://buildnewgames.com/real-time-multiplayer/) |
 | Design a garbage collection system | [stuffwithstuff.com](http://journal.stuffwithstuff.com/2013/12/08/babys-first-garbage-collector/)<br/>[washington.edu](http://courses.cs.washington.edu/courses/csep521/07wi/prj/rick.pdf) |
@@ -1699,11 +1699,10 @@ Handy metrics based on numbers above:
 
 * [Airbnb Engineering](http://nerds.airbnb.com/)
 * [Atlassian Developers](https://developer.atlassian.com/blog/)
-* [Autodesk Engineering](http://cloudengineering.autodesk.com/blog/)
 * [AWS Blog](https://aws.amazon.com/blogs/aws/)
 * [Bitly Engineering Blog](http://word.bitly.com/)
-* [Box Blogs](https://www.box.com/blog/engineering/)
-* [Cloudera Developer Blog](http://blog.cloudera.com/blog/)
+* [Box Blogs](https://blog.box.com/blog/category/engineering)
+* [Cloudera Developer Blog](http://blog.cloudera.com/)
 * [Dropbox Tech Blog](https://tech.dropbox.com/)
 * [Engineering at Quora](http://engineering.quora.com/)
 * [Ebay Tech Blog](http://www.ebaytechblog.com/)
@@ -1726,14 +1725,14 @@ Handy metrics based on numbers above:
 * [Microsoft Python Engineering](https://blogs.msdn.microsoft.com/pythonengineering/)
 * [Netflix Tech Blog](http://techblog.netflix.com/)
 * [Paypal Developer Blog](https://devblog.paypal.com/category/engineering/)
-* [Pinterest Engineering Blog](http://engineering.pinterest.com/)
+* [Pinterest Engineering Blog](https://medium.com/@Pinterest_Engineering)
 * [Quora Engineering](https://engineering.quora.com/)
 * [Reddit Blog](http://www.redditblog.com/)
 * [Salesforce Engineering Blog](https://developer.salesforce.com/blogs/engineering/)
 * [Slack Engineering Blog](https://slack.engineering/)
 * [Spotify Labs](https://labs.spotify.com/)
 * [Twilio Engineering Blog](http://www.twilio.com/engineering)
-* [Twitter Engineering](https://engineering.twitter.com/)
+* [Twitter Engineering](https://blog.twitter.com/engineering/)
 * [Uber Engineering Blog](http://eng.uber.com/)
 * [Yahoo Engineering Blog](http://yahooeng.tumblr.com/)
 * [Yelp Engineering Blog](http://engineeringblog.yelp.com/)