Are server actions guaranteed to run in succession?

[codinginflow]

I have this code in my app that uses a server action to create a new (anonymous ) shopping cart if the visitor clicks an "add to cart" button and no cart for them exists yet:

"use server";

import ...

export async function incrementProductQuantity(
  productId: string,
) {
  const session = await getServerSession(authOptions);

  const cart = (await getCart(session)) ?? (await createCart(session));

  ...add item...

  revalidatePath("/products/[id]");
}

I was worried about race conditions when the button is clicked multiple times and it would create multiple new carts. But when I tried it out, the server action wasn't executed multiple times in parallel, but one after another.

So do server actions always execute in succession or is my thinking wrong here?

[bigoldcat123]

export const write_unsafe = async (_name:string) => {
    console.log('write_unsafe',_name);

    const r = await db.data_teacher.findFirst({
        where:{
            name:_name
        }
    })
    console.log(r);
    if(r) {return 'exist'} 
    console.log('write -> ',_name);
    
    await new Promise(resolve => setTimeout(resolve, 3000))
    const t = await db.data_teacher.create({
        data:{
            name:_name
        }
    })
    return t.name
}

---result---

write_unsafe hello
null
write -> hello
write_unsafe hello
null
write -> hello
POST /dashboard/1996070003/650d4983-86e2-11ef-8e30-0242ac110002 200 in 3088ms
POST /dashboard/1996070003/650d4983-86e2-11ef-8e30-0242ac110002 200 in 3031ms

I guess it is not successive😭