would mysql js pool cause transaction deadlock - mysql

Question

I am designing an ticket system using NodeJS and Mysql-Promise.
For safety and consistency, I want to use Transaction but I worry about the deadlock.
The scenario is
People can buy multi tickets in one order
I would check every tickets whether the rest amount of tickets is enough or not.
I update the amount of tickets
I create the order
The code is
await ctx.conn.beginTransaction()
// check amount of tickets
let ticketIdList = ctx.body.tickets.map(t => t._id)
let ticketList = await models.ticket.findTicketList(ctx.conn, ticketIdList)
for (let t in ticketList) {
let ticketBook = ctx.body.tickets.filter(tB => tB._id === t._id)
if (t.perMinSaleCount > ticketBook.count || t.perMaxSaleCount < ticketBook.count) {
ctx.stats = 400
return ctx.body = {
error: "FailTickets"
}
}
if (t.sold + ticketBook.count > t.total) {
ctx.stats = 400
return ctx.body = {
error: "SoldOut"
}
}
}
// update the tickets
await Promise.all(
ctx.body.tickets.map(t => models.ticket.reserveTicket(ctx.conn, t._id, t.count))
)
// create Order
await model.order.createOrder(...)
await ctx.conn.commit()
My big concern is the ctx.conn is create by pool
mysql.createPool({
......
})
Would // await Promise.all(ctx.body.tickets.map(t => models.ticket.reserveTicket(ctx.conn, t._id, t.count))) this lines make sql in multi connections and cause deadlock ?
How to properly use conn.beginTransaction()?
Thanks