High-level design

We employ a simple design where the request a client makes is first forwarded to a Load Balancer, the load balancer balances load using the Round Robin scheme to find the best server for handling the request. The request then reaches the appropriate application server.
The application server then checks a URL cache to see if the result is present in the cache, returns the response if it is, otherwise, we check the database. Since we are going to be doing more reads than writes here, we use Redis, which is an in-memory non relational database that utilizes a single leader replication scheme to serve fast reads. As our caching policy, we use Least Recently Used.
The write flow would be pretty similar to this

flowchart TD

B["Client"];

C{"Load Balancer"};

D["Application Server"];

E["Redis Cache"];

F["PostgreSQL Database"];

B --> C;

C --> D;

D --> E;

D --> F;