Before I did this, it worked, backend got a HTTP response.

const programId = programIds[0]
await res.unstable_revalidate(`/hu/buyTicket/${programId}`)
return res.json({ revalidated: true })

but for multiple call, I get error:

Promise.all(
    programIds.map(
        async (programId: string) =>
            await res.unstable_revalidate(`/hu/buyTicket/${programId}`)
    )
).then((res) => {
    return res.json({ revalidated: true })
})

Error:

Property 'json' does not exist on type 'any[]'