đŸ”„ The DB Grill đŸ”„

Where database blog posts get flame-broiled to perfection

3 “Lightbulb Moments” for Better Data Modeling
Originally from mongodb.com
September 15, 2025 ‱ Roasted by Sarah "Burnout" Chen Read Original Article

Right, a "Lightbulb Moment." Let me tell you about my lightbulb moments. They usually happen around 3:17 AM. The lightbulb isn't a brilliant flash of insight; it's the harsh, fluorescent glare of my kitchen light as PagerDuty screams a lullaby of cascading failures. And it’s always, always because someone had a brilliant "lightbulb moment" six months ago after reading an article just like this one. "Pure, unadulterated excitement," it says. The only thing pure and unadulterated in that moment is the panic.

So, let's see what fresh hell this new "blog series" is promising to save us from.

First up, "Schema validation and versioning: Flexibility with control." Oh, this is my favorite. For years, the sales pitch was "It's schemaless! Think of the freedom!" which translated to production as, "Good luck figuring out if user_id is a string, an integer, or a deeply nested object with a typo in it." Now, the brilliant lightbulb is that maybe, just maybe, having some structure is a good idea. Groundbreaking.

They boast about schema validation like it’s a new invention, not a feature that every relational database has had since the dawn of time. But the real gem is schema versioning.

Gradually evolve your data schema over time without downtime or the need for migration scripts.

I just
 I have to laugh. The PTSD is kicking in. I see this and I don't see "no migration scripts." I see my application code turning into a beautiful museum of conditional logic. if (doc.schemaVersion === 1) { ... } else if (doc.schemaVersion === 2) { ... } else if (doc.schemaVersion === 3 && doc.contactInfo.cell) { ... }. It’s not a database feature; it's just outsourcing the migration headache to the application layer, where it will live forever, confusing new hires until the heat death of the universe. That "60x performance improvement" they mention? I guarantee the "before" schema was designed by an intern who took the "schemaless" pitch a little too literally. You could get a 60x performance improvement on that by storing it in a text file.

Next, the "Aggregation pipeline framework: Simplifying complex data queries." They say SQL JOINs are slow and expensive. You know what else is slow and expensive? A 27-stage aggregation pipeline that looks like a JSON ransom note, written by someone who thought "visual query building" was a substitute for understanding data locality. It's easier to debug, they claim. Sure. It's easy to debug stage one. And stage two. And stage three. It's only when you get to stage seventeen, at 2 AM, that you realize the data you needed was filtered out back in stage two because of a subtle type mismatch that the "flexible" schema allowed. Instead of one complex, understandable SQL query, I now have a dozen tiny, black-box processing steps. It’s not simpler; it's just complexity, but now with more steps. Progress.

But this
 this is the masterpiece. The grand finale. The Single Collection Pattern.

My god. They’ve done it. After decades of database normalization theory, of separating concerns, of painstakingly crafting relational models to ensure sanity and data integrity, the grand "lightbulb moment" is to just
 throw it all in one big box.

A more efficient approach is to use the Single Collection Pattern.

Let me translate: "Are you tired of thinking about your data model? Well, have we got the pattern for you! Just dump everything—books, reviews, users, the user’s great-aunt’s book club meeting notes—into one massive collection. Then, add a docType field to remember what the hell each document is supposed to be."

Congratulations. You’ve reinvented a single, giant, unmanageable table. But worse.

This isn't a lightbulb moment. This is the moment before the fire. It's the "let's just put everything in a global variable" of database design. I can already feel the future on-call incident brewing. The one where a single "book" with 50,000 "reviews" embedded or linked in the "junk drawer" collection brings the entire application to its knees.

So yeah. Thanks for the lightbulb. I’ll add it to the pile of broken bulbs from the last five "game-changing" solutions I've had to clean up after. This won't solve our problems. It'll just create new, more excitingly undocumented ones. Now if you’ll excuse me, my pager is having a sympathy panic attack just from me reading this.