The "Excel" Exorcism

There is a specific kind of chaos that comes from running a successful mobile car wash business using only a WordPress landing page, a phone number, and a shared Excel spreadsheet.

"Car Wash From Home" (CWFH) was growing fast, but their backend operations were stuck in 2010. Double bookings were common, customers had to call to find an open slot, and the admins were spending their evenings manually reconciling paper notes with digital spreadsheets.

They needed to stop playing "Tetris" with appointments and start automating.

Contents

• The Mission
• The Solution: More Than Just a Date Picker
• The Technical Deep Dive
  • The Schema Strategy
    • Structuring Complexity
  • The Logic
• The Results
• Conclusion

The Mission

I was brought in to perform a complete digital overhaul. The goal was simple but ambitious: kill the spreadsheet, modernize the brand, and build a booking brain that could handle the nuances of a real-world workforce.

The Solution: More Than Just a Date Picker

A generic booking plugin wouldn't cut it. CWFH needed logic that understood that humans need lunch breaks, that Christmas exists, and that sometimes a van breaks down on a Tuesday.

I built a custom solution centered around granular availability control.

The Technical Deep Dive

The UI was the fun part, but the database was the headache. Designing a schema that is performant enough to query availability in real-time, while being flexible enough to handle "Standard Tuesdays" vs "Christmas Eve Tuesday," required a complex relational structure.

I settled on a 5-table architecture (appointments, business-hours, recurring-time-slots, slot-exceptions, adhoc-time-slots) to decouple "Time" from "Availability."

A high-level view of the schema separating Business Rules from Actual Appointments.

The Schema Strategy

Structuring Complexity

We couldn't just have an appointments table. We needed to define the "Potential" for appointments first.

• business-hours: Defines the recursive weekly template for standard opening hours.

• recurring-time-slots: Represents normalized, recurring availability derived from the weekly template.

• slot-exceptions: Handles specific-date overrides (Holidays, Sick leave, one-off closed days).

• adhoc-time-slots: Fixed, ad-hoc intra-day blocks (Lunch, shift changes, temporary capacity adjustments).

• appointments: The actual committed slots.

The Logic

Here is a simplified look at how we calculate slots. We don't store "free slots" in the DB; we calculate them on the fly to ensure atomic accuracy.

// Simplified logic for generating availability
async function getAvailableSlots(date: Date, serviceDuration: number) {
  // 1. Fetch Master Rules (business-hours), recurring time slots and slot-exceptions (Holidays or one-offs)
  const rules = await prisma.businessHours.findMany({ ... });
 
  // 2. Fetch existing appointments for that specific day
  const appointments = await prisma.appointment.findMany({
  where: { date: date }
  });
 
  // 3. Generate all possible time chunks (e.g., 09:00, 09:30...)
  const potentialSlots = generateTimeChunks(rules);
 
  // 4. Filter out collisions
  return potentialSlots.filter(slot => {
  return !isOverlapping(slot, appointments) && !isDuringBreak(slot);
  });
}

The Results

We launched the new platform just before the spring rush. The impact was immediate. The phone stopped ringing off the hook, not because customers left, but because they were happily booking online at 11 PM.

Conclusion

This project proved that for local businesses, a custom solution isn't vanity—it's necessary efficiency. Moving from WordPress to a Serverless Next.js architecture didn't just make the site look pretty; it fundamentally changed how the company operates.

And honestly? I don't miss migrating data from Excel one bit. 😴

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