I decided to run a quick test to see just how much caching matters in a WordPress. I ran this test against a stock WordPress 3.8 install running Twenty Fourteen using Siege. I used the base nginx config from Varying Vagrant Vagrants. The site was loaded with the Theme Test Data so it had more than one post.

I did three test runs, all of them using 100 concurrent users requesting the homepage 100 times for a total of 10000 page loads.

The first test run was a completely stock WordPress install.

Transactions:		         569 hits
Availability:		       34.19 %
Elapsed time:		      499.20 secs
Data transferred:	       30.00 MB
Response time:		       27.48 secs
Transaction rate:	        1.14 trans/sec
Throughput:		        0.06 MB/sec
Concurrency:		       31.33
Successful transactions:         569
Failed transactions:	        1095
Longest transaction:	       30.01
Shortest transaction:	        0.00

As we can see, it didn’t take long for the site to fail. Only 569 requests succeeded.

Next I enabled the memcached plugin and setup memcached (with the stock VVV memcached config).

Transactions:		        1047 hits
Availability:		       49.76 %
Elapsed time:		      629.86 secs
Data transferred:	       58.56 MB
Response time:		       28.51 secs
Transaction rate:	        1.66 trans/sec
Throughput:		        0.09 MB/sec
Concurrency:		       47.40
Successful transactions:        1047
Failed transactions:	        1057
Longest transaction:	       30.07
Shortest transaction:	        1.04

Almost double the number of transactions succeeded, but we still brought the server down.

Finally, I enabled batcache as a full page cache.

Transactions:		       10000 hits
Availability:		      100.00 %
Elapsed time:		      110.76 secs
Data transferred:	      593.44 MB
Response time:		        1.10 secs
Transaction rate:	       90.29 trans/sec
Throughput:		        5.36 MB/sec
Concurrency:		       99.56
Successful transactions:       10000
Failed transactions:	           0
Longest transaction:	        3.26
Shortest transaction:	        0.54

100% Success! You will also notice that this run took less than 20% of the time as my previous attempt where only ~1/10 of the requests succeeded.

Moral of the story: WordPress + Memcached + Batcache = Win!