Route handlers are pretty nice, if you need external api access. Like that you can build a backend for others, that they can use.

As you said: server actions can be used to remove the complicated route handlers, because server actions are easy to setup, but can't be externally used.

Calling a method inside server side code is the most common approach for me, when it comes to data fetching

by using route handler to fetch data, sometime, just do the same things again in the handler as what we do in client side; for example,
In client component:
const AComponent: React.FC = ()=> {
useEffect(()=> {
fetch('api/text', {}).then(()=> {}).catch((err)=>{});
}, []);
}

In the api/test directory:
const POST = async()=> {
fetch(apiEndPoint, {}).then(()=> {}).catch((err)=> {});
}

base on the code above, two parts of code almost the same.

however, if we use server action directly in client component.
const AComponent: React.FC = ()=> {
useEffect(()=> {
fetch('apiEndPoint', {}).then(()=> {}).catch((err)=>{});
}, []);
}
just type one time code and fetch the data.


so, base both the two methods, I am confusion how do I make a decision what option would we choose, whether server action or route handler or not

Do you need the endpoint to have external access?

the apiEndPoint is the backend api service which can visit database, some foundation service, however it may visit the exteral partner's service

So, does your endpoint (this: see attached) need external access?

I think, No! it is hidden behind the server. it's a backend service.

Thanks for the clear response. If you don't need external access, why do you want to create an endpoint, that is externally reachable.

But: we also need to consider, where you fetch your data. You are fetching it inside a client component. Fetching inside a client component is ok, but you might want to pass it from a server component directly down, to use server side fetching. Or if you don't want to use serverside fetching, you should use a client side library for fetching data like react query or swr.

So fetch data serverside and pass down as props. That's not possible no worries at all: get a client library and build your endpoint for data fetching. Fetch your own endpoint and the endpoint fetches from your external source.

If it's possible, you might want to fetch the external source directly from your client

I just draw a archtecture diagram to describe it.

Thank your for your kindly response, I am confusion about the mutations, how do I understand the words: mutations from client. Thanks again.

Imagine you build a ecommerce store and you handle your cart via your database. Then the client want to add something to his cart. The client clicks the button "add to cart". Now the client starts a mutation of the cart objects and mutates it correctly. It's initiated clientside. That's a mutation from the client

got,Thanks

sure thing. Is your question solved like that?