Performance

• Built - Algorithms / Big 0 | Linear vs Binary Search
• Fueled - Compute, Memory, Disk | Single vs Multi Core ...
• Tuned - GC Tuning, VM Args Heap -Xmx -Xms Suriver Ratio etc

Sometimes we and get it by Default

Don’t just turn off the cache. Let browser handle the HTTP Request cache-control Headers

GET /welcome/ HTTP/1.1
If-Modified-Since: Mon, 26 Jul 1997 05:00:00 GMT
Cache-Control: no-cache
Pragma: no-cache
      

Who is turning OFF the HTTP cache? Most often it's not Client side

• Alice the User doesn't know about cahcing or even HTTP. She is just using her Chrome Browser
• Or if she left Caching disabled in Chrome Dev Tools?
• Alice the Developer without any need is disabling the HTTP Cache client side code or script

GET /welcome/ HTTP/1.1
If-Modified-Since: Mon, 26 Jul 1997 05:00:00 GMT
Cache-Control: no-cache no-store
Pragma: no-cache
        

Server Side is likely turning HTTP Caching OFF. But How and Why?

By default, Spring Security sets specific cache control header values for us, without us having to configure anything such that browser will never cache HTTP responses

            

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity
public class SpringSecurityConfig extends WebSecurityConfigurerAdapter {...}

@GetMapping("/default/users/{name}")
public ResponseEntity getUserWithDefaultCaching(@PathVariable String name) {
    return ResponseEntity.ok(new UserDto(name));
}

The resulting cache-control header will look like this:
[cache-control: no-cache, no-store, max-age=0, must-revalidate]

Conditional Get

Cache Coherency with Etag (content hash) | With If-modified-since (timestamp)

Cache but ensure Browser must revalidate before use

Browser will compare it with the server's version by sending the contents of Last-Modified or ETag, as you wanted.    
      

max-age=0 in Cache-Control header froces browser to recheck your cached-response with the server.

must-revalidate in Cache-Control header says that the cache may not serve this content when it is stale (i.e. "expired"), but must revalidate before that. Yes, caches (and browsers) can in theory be set to serve pages even if they are stale, though the standard says they should warn the user if they do this.

no-cache used to be that you could add instead, but as users have been expecting this to behave as no-store, browsers are gradually treating them the same.

Surprise....Yes it works in IE 6+

Why is HTTP Response Caching Important?

• Improve User Experience with Incresed Speed and Responsive
• Save Cost over unecessary Data Transfer
• Save Hardware Resources | (Compute, Memoery and Disk/DB Access)

• We cannot control how our clients will access our applications over the Internet
• Many of Clound Native Solutions are sharing resources. Pay per use
• ISPs are Monetizing over Usage not just connectivity

Governed by HTTP standard; Browser / Agents have gone through decards of evolution to make it work by default