Are the service metrics showing that the process isn't exceeding 1 vCPU?

it is 1-1.3

Programs aren't multi-threaded by default, you'd have to update your Next.js project to run your task in multiple threads

Will try, thank you!

Also, if you just upgraded recently to the Hobby plan, make sure to re-deploy your applications, as the new 8GB + 8vCPU limits only take effect after a re-deployment. If you've already done this, then refer to Astrid's answer.

Also, forgot to mention but you're also able to use Railway's replicas
https://docs.railway.com/reference/scaling#horizontal-scaling-with-replicas