Flash Sale Frenzy: How We Conquered Inventory Oversales in 15 Seconds

01/04/2024 | Technical Case Studies

In today's e-commerce landscape, stores have a dizzying array of database options at their fingertips. Cloud-based solutions, NoSQL databases, and powerful server setups offer tempting promises of scalability and resilience. Yet, for many businesses, especially those built on the bedrock of PHP and MySQL, the question remains: are these modern architectures truly necessary for handling the explosive traffic and demanding transactions of a flash sale?

So one of projects we are working on, during a recent flash sale, we encountered a critical inventory glitch: one popular product was seemingly oversold, with 153 units purchased despite a stock limit of 100. The incident, potentially impacting customer satisfaction and brand reputation, demanded immediate attention.

Thorough investigation revealed no anomalies in our inventory management system or the e-commerce platform's code. It wasn't until analyzing traffic patterns and payment gateway logs that the culprit emerged: processing delays by the third-party payment gateway. High flash sale traffic resulted in transaction processing times of 10 to 15 seconds, creating a critical gap. During this lag, multiple orders could register before the system acknowledged the first sale, leading to apparent overselling.

The challenge, therefore, wasn't the accuracy of our systems, but ensuring accurate real-time inventory reflection amidst payment processing delays. The solution we implemented drew inspiration from a familiar system: restaurant reservations.

Just as booking a table doesn't guarantee immediate seating, we introduced a "reserved stock" column within the database. This column reflects the number of items in limbo, awaiting payment confirmation. Now, when a customer initiates a purchase, the item is "reserved" even before the payment gateway processes the transaction.

The benefits of this system are two-fold:

  • Inventory accuracy: Regardless of processing delays, oversold situations are eliminated. If payment succeeds, the reserved item moves to the sold inventory and total stock is reduced. If payment fails, the reservation is released, and the item remains available.
  • Customer confidence: We can confidently display accurate stock levels even during high traffic periods, building trust and preventing frustration for customers who might otherwise encounter "out-of-stock" messages after completing the checkout process.

This innovative solution, inspired by real-world scenarios, goes beyond simply patching a technical glitch. It ensures a dynamic and accurate inventory management system, capable of handling unpredictable fluctuations in online traffic and payment processing times. Ultimately, it safeguards both our inventory and customer trust, solidifying our commitment to seamless and reliable e-commerce experiences.

I hope this business-style article effectively conveys your experience and solution. Feel free to tailor it further with specific details about the project and its impact on your company.

Logic Code Sample:

// Function to process a flash sale order
function processFlashSaleOrder(productId, quantity) {
  // Get product inventory
  const productInventory = getProductInventory(productId);

  // Check for available stock
  if (productInventory >= quantity) {
    // Reserved stock (not committed yet)
    reserveStock(productId, quantity);

    // Attempt to create order (may involve database transactions, payment processing, etc.)
    if (createOrder(productId, quantity)) {
      // Order successful, commit reserved stock
      commitStock(productId, quantity);
      return true; // Indicate success
    } else {
      // Order failed, release reserved stock
      releaseReservedStock(productId, quantity);
      return false; // Indicate failure
  } else {
    // Insufficient stock
    return false; // Indicate failure

Check this screenshot:
Imagine a queue of 6 pre-orders forming during a slow period. Now, factor in a 15-second delay for each order to clear the third-party payment gateway. This scenario highlights the importance of this concept in preventing overselling and its potentially negative consequences.

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