Steps for the Transaction

1. Start a client session
2. Define the transaction options (Optional)
3. Define the sequence of operations to perform inside the transactions
4. Release resources used by the transaction

<aside> ⚠️ Multi-document transactions have a 60-second time limit

</aside>

1. Create variables used in the transaction.

// Collections
const accounts = client.db("bank").collection("accounts")
const transfers = client.db("bank").collection("transfers")

// Account information
let account_id_sender = "MDB574189300"
let account_id_receiver = "MDB343652528"
let transaction_amount = 100

1. Start a new session.

const session = client.startSession()

1. Begin a transaction with the WithTransaction() method on the session.

const transactionResults = await session.withTransaction(async () => {
  // Operations will go here
})

1. Update the balance field of the sender’s account by decrementing the transaction_amount from the balance field.

const senderUpdate = await accounts.updateOne(
  { account_id: account_id_sender },
  { $inc: { balance: -transaction_amount } },
  { session }
)

1. Update the balance field of the receiver’s account by incrementing the transaction_amount to the balance field.

const receiverUpdate = await accounts.updateOne(
  { account_id: account_id_receiver },
  { $inc: { balance: transaction_amount } },
  { session }
)

1. Create a transfer document and insert it into the transfers collection.

const transfer = {
  transfer_id: "TR21872187",
  amount: 100,
  from_account: account_id_sender,
  to_account: account_id_receiver,
}

const insertTransferResults = await transfers.insertOne(transfer, { session })

1. Update the transfers_complete array of the sender’s account by adding the transfer_id to the array.

const updateSenderTransferResults = await accounts.updateOne(
  { account_id: account_id_sender },
  { $push: { transfers_complete: transfer.transfer_id } },
  { session }
)