ActiveRecord::SessionStore: Session vs SqlBypass
One Mongrel instance in production mode
$ ab -n 1000 -c 50 http://127.0.0.1:3000/session/read
$ ab -n 1000 -c 50 http://127.0.0.1:3000/session/write

Session
###############################################################################
### READ

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            3000

Document Path:          /session/read
Document Length:        1 bytes

Concurrency Level:      50
Time taken for tests:   10.747 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      287004 bytes
HTML transferred:       1000 bytes
Requests per second:    93.05 [#/sec] (mean)
Time per request:       537.368 [ms] (mean)
Time per request:       10.747 [ms] (mean, across all concurrent requests)
Transfer rate:          26.08 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.3      0      10
Processing:    14  528 196.3    506    1149
Waiting:       11  523 195.5    501    1146
Total:         14  529 196.2    506    1149

Percentage of the requests served within a certain time (ms)
  50%    506
  66%    515
  75%    533
  80%    560
  90%    667
  95%   1056
  98%   1143
  99%   1147
 100%   1149 (longest request)

### WRITE

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            3000

Document Path:          /session/write
Document Length:        2 bytes

Concurrency Level:      50
Time taken for tests:   10.011 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      330003 bytes
HTML transferred:       2000 bytes
Requests per second:    99.89 [#/sec] (mean)
Time per request:       500.527 [ms] (mean)
Time per request:       10.011 [ms] (mean, across all concurrent requests)
Transfer rate:          32.19 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1   2.4      0      12
Processing:    15  490 104.1    522    1036
Waiting:       10  485 104.6    517    1033
Total:         15  491 103.2    522    1037

Percentage of the requests served within a certain time (ms)
  50%    522
  66%    532
  75%    536
  80%    542
  90%    550
  95%    556
  98%    567
  99%    933
 100%   1037 (longest request)

SqlBypass
###############################################################################
### READ

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            3000

Document Path:          /session/read
Document Length:        1 bytes

Concurrency Level:      50
Time taken for tests:   7.531 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      287002 bytes
HTML transferred:       1000 bytes
Requests per second:    132.78 [#/sec] (mean)
Time per request:       376.571 [ms] (mean)
Time per request:       7.531 [ms] (mean, across all concurrent requests)
Transfer rate:          37.21 [Kbytes/sec] received

Connection Times (ms)
             min  mean[+/-sd] median   max
Connect:        0    0   0.9      0       7
Processing:    11  369  83.6    349     809
Waiting:        9  366  84.1    345     807
Total:         11  370  83.4    349     810

Percentage of the requests served within a certain time (ms)
 50%    349
 66%    415
 75%    421
 80%    426
 90%    435
 95%    443
 98%    460
 99%    741
100%    810 (longest request)

### WRITE

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            3000

Document Path:          /session/write
Document Length:        2 bytes

Concurrency Level:      50
Time taken for tests:   7.802 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      330001 bytes
HTML transferred:       2000 bytes
Requests per second:    128.17 [#/sec] (mean)
Time per request:       390.121 [ms] (mean)
Time per request:       7.802 [ms] (mean, across all concurrent requests)
Transfer rate:          41.30 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.1      0       8
Processing:    11  383  94.7    365     885
Waiting:        9  379  95.0    362     883
Total:         11  383  94.2    365     886

Percentage of the requests served within a certain time (ms)
  50%    365
  66%    432
  75%    435
  80%    437
  90%    453
  95%    560
  98%    579
  99%    738
 100%    886 (longest request)