- Learn AWS
- Architecture
- Classic three-tier
Architecture pattern
AWS Classic three-tier architecture
when a normal web application that has to stay up
The shape most enterprise applications actually are. A load balancer spreads traffic across instances in more than one Availability Zone, an Auto Scaling group replaces anything that dies, and a Multi-AZ database fails over without you. Unfashionable and completely correct for a stateful app you cannot rewrite.
What it runs through
In the order a request or a record moves through it. Each one links to the page that explains it.
Signals in a brief that point here
Phrases that, when you meet them in a scenario, mean this shape rather than another. They are the tell, and they are what an exam question is built around.
- “existing application”
- “lift and shift”
- “high availability”
- “cannot be rewritten”
- “long-lived connections”
What it costs you
You own the instances: patching, AMIs, capacity planning, and paying for them while they idle.
Every shape has one. A design decision with no stated downside is usually a decision nobody has finished making.
Learn the services in it
- AWS Route 53AWS's DNS service. It registers domains, answers queries for them with a choice of routing policies, and sends traffic away from endpoints that fail their health checks.
- AWS ELBSpreads incoming traffic across healthy targets in several Availability Zones, with four kinds of load balancer: Application, Network, Gateway and Classic.
- AWS Auto ScalingKeeps the right number of EC2 instances running. It replaces the ones that fail, and adds or removes instances as the load changes.
- AWS RDS and AuroraManaged relational databases: six engines run for you, plus Aurora, AWS's own MySQL- and PostgreSQL-compatible engine, with standbys, replicas and backups built in.
Shapes it is easily confused with
These run through some of the same services, which is exactly why a brief that fits one can look like it fits another.
Now build it from a brief
Reading a shape and producing one from a scenario that never names a service are different skills, and the exam asks for the second. The scenarios give you the brief; you draw the architecture and it is scored against what the brief requires.