I have bit understanding about AWS but not the full picture. If anyone can fill my gaps that will be good.

Suppose i have Web Application A, Using Amazon RDS B . I have queue in database so that all incoming requests add row in queue and that gets picked by my background process which picks jobs.

For one server its al right . i want to know how to architect that application so that it can scale using Load balancer and Auto scaling Group

My doubts are:

  1. I know that Auto scale group can make new instanaces of A in case of high load. But what about RDS . suppose i have 4 Ec2 instances but will RDS be only 1. If yes then how can RDS mange the load from 4 instances

  2. The other thiing is i have background process picking up tasks from Queue table. how can they scale with instances. Any idea on how can i get better picture on that


SF isn't really for architectural advice, but I'll give you some general ideas:

  • Using an actual queuing system (SQS) rather than a database would be more reliable. If you keep using RDS it's probably ok, just lock the table before you retrieve the next job in the "queue".
  • Set up auto scaling based on queue size. Read the documentation for how. You can also scale based on CPU usage of the instance.
  • Scale your web application with an elastic load balancer
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  • Thanks , i got that , but as i see that scaling of ec2 will work but , how does RDS keep up with scaling . like suppose i have 100 instances of web appliation , but will the RDS be only one . how Single RDS can handle requests from 100 servers – Karl Mar 9 '16 at 22:07
  • RDS is just a dedicated server, essentially. You can easily move to a larger instance, which is typically done during your maintenance window, but that involves downtime. You could also add read replicas, if it's a read heavy workload. A multi-AZ deployment may work around the downtime issue, but you'd have to check. Otherwise search for "how scale RDS without downtime" or similar, which should give you some ideas. – Tim Mar 9 '16 at 23:58

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