Lesson 6
Why read replicas?
Break it
A social feed with a cache. Turn traffic up to 3,000 requests per second.
Users
1,500 req/s
Load balancer
splits evenly
3%
App servers
× 4
39%
Cache
30% hit rate
1%
DB primary
reads + writes
76%
Read replicas
None
Off
p50 latency
209 ms
Failed requests
0.0%
Monthly cost
$360