E-COMMERCE ENGINE

1// Distributed inventory reservation using atomic Lua transactions
2export async function reserveStock(
3  sku: string,
4  brandId: string,
5  quantity: number
6): Promise<ReservationResult> {
7  const key = `stock:${brandId}:${sku}`;
8
9  // Atomic decrement — Redis handles concurrency
10  const remaining = await redis.eval(`
11    local stock = tonumber(redis.call('GET', KEYS[1]))
12    if stock == nil or stock < tonumber(ARGV[1]) then
13      return -1
14    end
15    return redis.call('DECRBY', KEYS[1], ARGV[1])
16  `, 1, key, quantity);
17
18  if (remaining === -1) {
19    throw new InsufficientStockError(sku, brandId);
20  }
21
22  return { reserved: quantity, remaining };
23}