After you send, poll the receipt to see whether APNs or FCM accepted the message:

const receipt = await client.getReceipt(ticket.id);

if (receipt.status === "delivered") {
  console.log("● delivered");
} else if (receipt.status === "failed") {
  console.log("● failed:", receipt.error);
  if (receipt.tokenInvalid) {
    // Remove the token from your database
  }
}