Overriding handle function in a custom server

[markushav]

I'm building an Express webserver including a simple backend and a NextJS frontend that can serve multiple different sites with many different URLs. The idea is that the service scales automatically in a basic Google App Engine I've set up. Basically one server instance can serve as a frontend or backend for any site (around 5-10 sites in the beginning) depending on where there is a need and then when GAE decides there's too much load, it can automatically assign another server instance that can help in whatever needed for any of the sites.

I've made a decision to have all my data in a NoSQL cloud storage and fetch the data dynamically in getServerSideProps. I want to control all paths dynamically in my database so I've put app.render() in the server.get('*' ... wildcard route with using handle() function only when necessary. I've concluded that I need to use the handle() in three scenarios:

1. If the path is an internal NextJS path (starting /_next/) or
2. the path refers to a file that is present in the /public/ folder or

3. the path refers to a hardcoded site template (there is a .tsx or .jsx corresponding the path in pages folder).

Are there any other situations where I should to use the handle() function?

Also please share your thoughts if you think I am overcomplicating this or if there is something else that comes to mind! Thanks!

server.ts:

import next from 'next'
import bodyParser from 'body-parser'
import { getPage, parseCurrentSite } from './lib'
import fs from 'fs'

const port = process.env.PORT ? process.env.PORT : 5555
const dev = process.env.NODE_ENV !== 'production'
const app = next({ dev })
const handle = app.getRequestHandler()

app.prepare().then(() => {
    const server = express()
    server.use(bodyParser.json())

    server.get('/backend/data', async (req: express.Request, res: express.Response) => {
        const query = req.query
        const site = parseCurrentSite(req)
        const { path } = req.query
        if (typeof path !== 'string') throw 'Invalid path'
        const page = await getPage(site, path)

        return res.status(200).send(page)
    })

    server.get('*', (req: express.Request, res: express.Response) => {

        const isInternalNextJSPath = req.path.startsWith('/_next/')
        const isFileInPublicFolder = fs.existsSync('./public' + req.path)
        const isHardcoded = ['.tsx', '.jsx', '.js'].reduce((isHardcoded, fileExtension) => {
            isHardcoded = isHardcoded ||
                fs.existsSync('./pages' + req.path + fileExtension) ||
                fs.existsSync('./pages' + req.path + '/index' + fileExtension)
            return isHardcoded
        }, false)

        if (
            isInternalNextJSPath ||
            isFileInPublicFolder ||
            isHardcoded
        ) {
            return handle(req, res)
        }

        return app.render(req, res, '/')
    })

    server.listen(port, () => {
        console.log(`App listening on port ${port}`)
    })
})

pages/index.tsx:

import { Response, Request } from 'express'

const Page = ({data}) => <div>Renders the page with the {JSON.stringify(data)}</div>

export const getServerSideProps = async (context: {
    req: Request,
    res: Response
}) => {
    const { req } = context
    const { host } = req.headers
    const isLocal = host.includes('localhost')
    const protocol = isLocal ? 'http:' : 'https:'
    const origin = `${protocol}//${host}`

    const data = await axios.get(`${origin}/backend/data?path=${req.path}`).then(response => response.data)

    return { props: { data } }
}

export default Page