How To Implement A Better Build Strategy for Next.js App - deployment

Question

I am hosting a Next.js app on digitalocean and managing it as a process using pm2.
Everything is working well except when I am pushing changes to server. Both create react app and Next.js are unavailable at build time, nginx return a server error or not found error when building the apps. When using create react app I would build the files on my local computer and send them to the server using ssh which allowed for quicker updates. I can't see how the same is possible with Next.js.
My main problem is how I can still build the Next.js while still making the previous build available until the current build is complete.

Answer 1

make one bash script and insert condition
if name "a" folder is available then create "b"
elif if name "b" folder is available then create "a"
else create name "a" folder
if name "A" folder available then create name "b" folder and run all commands on name "b" folder like "npm i " npm run build " after complete of execution . then delete name "a" folder then run pm2 stop appname then go through name "b" folder and run pm2 start
thease all commands run through bash script