Elastic Load Balancers
NLB
Operates at Layer 4, TCP/UDP
Ultra-low latency
Can handle tens of millions of requests per second while maintaining high throughput at ultra-low latency
ALB
Operates at Layer 7, HTTP, HTTPS
You can create a listener rule on the ALB to redirect HTTP traffic to HTTPS.
ALB supports path-based routing (route the traffic to different target group based on the url/path)
Session Management
Sticky sessions or session affinity (local)
route a site user to the particular web server that is managing that individual user’s session
it’s cost effective, generally fast because it eliminates network latency
Drawback:
In the event of node failure, session data is lost,
If using ASG, traffic may be unevenly distributed
Distributed Session
ElastiCache for Redis, and ElastiCache for Memcached
Provide a shared data storage for sessions that can be accessible from any individual web server
There is additional cost and network latency
These are extremely fast and provide sub-millisecond latency
Can cache any data, not just HTTP sessions
