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Jairo Junior
Jairo Junior

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Cache-Control: the silent hero in communication between services

When people talk about performance, scalability, or even costs, they usually jump straight to:

  • bigger machines
  • more replicas
  • faster databases
  • more complex architectures

But there’s one HTTP detail that is almost always underestimated and, at the same time, insanely powerful:

👉 Cache-Control

If you work with communication between different apps (frontend ↔ backend, backend ↔ backend, BFFs, APIs, gateways, etc.), understanding cache-control can save you latency, money, and a lot of pain.


The problem we usually ignore

In many systems, requests look like this:

  • App A calls App B
  • App B calls App C
  • App C hits a database or an external API

And this happens all the time, even when:

  • the data barely changes
  • the response is identical for minutes (or hours)
  • thousands of users are requesting the same thing

So we end up doing:

  • repeated network calls
  • repeated serialization/deserialization
  • repeated DB reads

All for the same response.

That’s not just inefficient — it’s unnecessary.


Where Cache-Control fits in

Cache-Control is an HTTP header that tells the consumer how long a response can be reused and under which conditions.

And the beauty of it is:

✅ it’s standardized
✅ it works across different apps and languages
✅ it doesn’t require shared memory or tight coupling

You’re basically saying:

“Hey, this response is safe to reuse for X seconds.”

And suddenly, a lot of things get faster without changing your core logic.


A simple example

Imagine an API that returns configuration data:

GET /configs
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The response rarely changes.

Instead of forcing every client to hit the API every time, you return:

Cache-Control: public, max-age=300
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Now:

  • browsers can cache it
  • gateways can cache it
  • reverse proxies can cache it
  • other backend services can cache it

For 5 minutes, everyone can reuse the same response.

No extra code.
No extra infra.
Just a header.


Cache between backend services? Yes, please.

A common myth is:

“Cache-Control is just for browsers.”

Not true.

When you have:

  • microservices
  • BFFs
  • API gateways
  • edge services

Cache-Control becomes a contract between services.

App B doesn’t need to guess:

  • if it can cache
  • for how long
  • or if it should revalidate

The producer tells the truth, and the consumer follows it.

That’s clean communication.


Performance is not the only win

1. Lower latency

Cached responses are usually served in microseconds, not milliseconds.

2. Lower cost

Fewer requests:

  • less CPU
  • fewer DB hits
  • fewer external API calls

That shows up directly on the bill.

3. Better resilience

When downstream services are slow or unstable, cached responses can:

  • absorb traffic spikes
  • reduce pressure during incidents
  • keep the system usable even under partial failure

Sometimes cache is the difference between:

“the system is degraded”
and
“everything is on fire 🔥”


Cache-Control is also about correctness

Cache is not only about speed.

Headers like:

  • no-cache
  • no-store
  • private
  • must-revalidate

allow you to be explicit about what should not be cached.

That avoids:

  • stale sensitive data
  • user-specific leaks
  • weird bugs caused by over-caching

Good cache-control is about control, not just caching everything.


A practical rule of thumb

If an endpoint:

  • returns the same response for many users
  • doesn’t change on every request
  • is expensive to compute
  • is called frequently

👉 it probably deserves a Cache-Control header.

Even a small max-age=30 can make a noticeable difference.


Why this matters more in distributed systems

As systems grow, communication cost becomes real:

  • network hops
  • retries
  • timeouts
  • cascading failures

Cache-Control helps you reduce unnecessary conversations between services.

And in distributed systems, fewer conversations usually means:

  • fewer problems
  • simpler reasoning
  • better sleep at night 😄

Final thoughts

Cache-Control is not fancy.
It won’t show up in architecture diagrams.
It won’t impress in a meetup slide.

But it works.

And when you start using it intentionally, you realize something important:

Sometimes the biggest performance gains come from saying
“you don’t need to call me again… not yet.”

If you’re building APIs and not thinking about Cache-Control, you’re leaving performance and reliability on the table.

And that’s an easy win you don’t want to miss. 🚀


Se quiser, posso escrever um follow-up com:

  • exemplos práticos de headers (ETag, If-None-Match, stale-while-revalidate)
  • cache-control em APIs privadas vs públicas
  • como usar isso bem com gateways e CDNs

Perfeito 😄
Aqui está o artigo no mesmo estilo humano, direto, dev-to-dev, pronto pra mandar pro dev.to:


Cache-Control: the silent hero in communication between apps

When people talk about performance, scalability, or system reliability, the conversation usually goes straight to:

  • more replicas
  • bigger instances
  • better databases
  • more complex architectures

But there’s one thing that is often ignored and delivers huge impact with almost zero effort:

👉 Cache-Control

If you work with communication between different applications — frontend ↔ backend, backend ↔ backend, BFFs, APIs, gateways — this header can change the game.


The problem nobody questions

In a lot of systems, the flow looks like this:

  • App A calls App B
  • App B calls App C
  • App C hits a database or an external API

And this happens over and over again, even when:

  • the data barely changes
  • the response is exactly the same
  • thousands of users are requesting identical information

So we keep paying the cost of:

  • network calls
  • serialization
  • CPU
  • database reads

All for data we already had a few seconds ago.

That’s not a scaling problem.
That’s a communication problem.


Where Cache-Control fits in

Cache-Control is an HTTP header that tells the consumer how a response can be reused and for how long.

And the best part:

  • it’s standardized
  • language-agnostic
  • works across different apps and teams
  • doesn’t require shared state

You’re basically saying:

“This response is safe to reuse for X seconds.”

And suddenly, a lot of unnecessary traffic just disappears.


A very simple example

Imagine an endpoint that returns configuration or static metadata:

GET /configs
Enter fullscreen mode Exit fullscreen mode

The data changes maybe once every few minutes.

Instead of forcing every client to call it every time, you return:

Cache-Control: public, max-age=300
Enter fullscreen mode Exit fullscreen mode

Now, for 5 minutes:

  • browsers can cache it
  • API gateways can cache it
  • reverse proxies can cache it
  • other backend services can cache it

Same response.
Zero extra calls.
Just one header.


“But this is only for browsers”, right?

Nope.

This is one of the biggest misconceptions.

In systems with:

  • microservices
  • BFFs
  • internal APIs
  • edge services

Cache-Control becomes a contract between services.

The producer explicitly says:

  • if the response can be cached
  • for how long
  • under which conditions

The consumer doesn’t need to guess.
That’s clean and intentional communication.


Performance is just one benefit

1. Lower latency

Cached responses are served almost instantly.
That’s noticeable — especially at scale.

2. Lower costs

Fewer calls mean:

  • less CPU
  • fewer DB hits
  • fewer external API requests

Your cloud bill will thank you.

3. Better resilience

During incidents or traffic spikes, cache can:

  • absorb load
  • reduce pressure on downstream services
  • prevent cascading failures

Sometimes cache is the difference between:

“the system is slow”
and
“everything is down 🔥”


Cache-Control is also about safety

Cache is not just about caching everything.

Directives like:

  • no-store
  • no-cache
  • private
  • must-revalidate

exist to make things explicit.

They help you avoid:

  • leaking user-specific data
  • serving stale sensitive information
  • weird bugs caused by accidental caching

Good cache-control is about being intentional, not aggressive.


A simple rule that works

If an endpoint:

  • returns the same data for many users
  • doesn’t change on every request
  • is expensive to compute
  • is called frequently

👉 it probably deserves a Cache-Control header.

Even something small like max-age=30 can already reduce a lot of noise in your system.


Why this matters even more in distributed systems

As systems grow, communication becomes expensive:

  • more hops
  • retries
  • timeouts
  • failure propagation

Cache-Control helps you reduce unnecessary conversations between services.

And fewer conversations usually mean:

  • fewer bugs
  • simpler mental models
  • better nights of sleep 😄

Final thoughts

Cache-Control isn’t flashy.
It won’t show up in architecture diagrams.
It won’t impress in slides.

But it works.

And once you start using it properly, you realize something important:

Sometimes the biggest performance gain is simply saying:
“You don’t need to call me again… not yet.”

If you’re building APIs and ignoring Cache-Control, you’re leaving performance, resilience, and money on the table.

And that’s one of the easiest wins you can get. 🚀

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