Transactions & Data Integrity¶

Some operations touch multiple rows and must succeed or fail as one unit. That's a transaction.

The Classic Example¶

Transferring credits from one account to another is two writes:

If the server crashes between step 1 and 2, money vanishes. A transaction guarantees both happen or neither does.

1await prisma.$transaction([
2  prisma.account.update({ where: { id: a }, data: { balance: { decrement: 100 } } }),
3  prisma.account.update({ where: { id: b }, data: { balance: { increment: 100 } } }),
4]);

Interactive Transactions for Logic¶

When later steps depend on earlier ones, use the callback form:

1await prisma.$transaction(async (tx) => {
2  const order = await tx.order.create({ data: { userId, total } });
3  for (const item of items) {
4    await tx.orderItem.create({ data: { orderId: order.id, ...item } });
5    await tx.product.update({
6      where: { id: item.productId },
7      data: { stock: { decrement: item.qty } },
8    });
9  }
10});

If any step throws, the whole thing rolls back — no half-created orders, no negative stock.

ACID in One Breath¶

Keep Transactions Short¶

A transaction holds locks. Don't call external APIs, send emails, or do slow work inside one — do that after it commits. Long transactions block other writers and cause deadlocks.