Some posts from a new job Assessment

Publicado: enero 15, 2012 en Sin categoría

One year ago I applied for a Linux engineer position in a Internet company abroad.

They did send me a technical assessment with several questions. I took it quite seriously and I did the best I could. Sadly I did not get the job, but I did learn a lot from this.

This was time ago, and now I feel that I can publish some of these replies, they might they are useful for somebody, even as anti-pattern.

One thing that was annoying is that they did not describe the platform enough, and I did have to make a lot of assumptions. But the intention was evaluate me, not implement real solutions.

Webserver architecture assumptions

To reply the questions, specially OS and PHP version control and Redundant load balancer design, the webserver architecture must be considered. I will design the solutions for the following architecture:

  • The servers are located in different physical datacenters or sites. I will consider 4 sites.
  • The webservers are grouped in farms. Farms members should in the same subnet,
    connected to an high-performance local network, but on different hardware.
    I will consider 16 servers per farm.
  • The architecture has a mechanism to share the sessions. For instance we can consider:
    • memcached stored sessions.
      • One memcached server per webserver.
      • One memcached cluster per farm.
    • DB backend for the sessions (for sessions it is good a NoSQL DB).
      • One DB backend by site. Any webserver recover a session created in the site.
        It is possible to configure an inter-site replication.
      • It must offer redundancy and HA.
  • Other caches implemented can follow the same schema.

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