You have a business-critical two-tier web app currently deployed in two AZs in a single region, using Elastic
Load Balancing and Auto Scaling. The app depends on synchronous replication (very low latency connectivity)
at the database layer. The application needs to remain fully available even if one application AZ goes off-line,
and Auto Scaling cannot launch new instances in the remaining Availability Zones. How can the current
architecture be enhanced to ensure this?
A.
Deploy in two regions using Weighted Round Robin (WRR), with Auto Scaling minimums set for 50 percent
peak load per Region.
B.
Deploy in two regions using Weighted Round Robin (WRR), with Auto Scaling minimums set for 100
percent peak load per region.
C.
Deploy in three Availability Zones, with Auto Scaling minimum set to handle 50 percent peak load per zone.
D.
Deploy in three Availability Zones, with Auto Scaling minimum set to handle 33 percent peak load per zone.
C
Deploy in three Availability Zones, with Auto Scaling minimum set to handle 50 percent peak load per zone.
Choice A give 33%, 33% , 33% load, one goes down, I am left with two to handle 66% load. what about rest 36%? Remeber the question says autoscaling is not working. This is not the answer.
Choice B – as far as I know WRR is not an option for DNS routing
Choice C – Same justification as A and B
Choice D – 50%, 50%, 50% – One does down, auto scaling is failing. No issues, still 50% + 50% LB handles all my load. So D is the answer.
D is wrong as in this case, if one AZ goes down, it can handle only 33%+33%