Playground
22 schemas from products you already know, open on a real canvas. Drag anything, switch the view, add a model, export it. No account, and nothing here saves — it resets the moment you reload.
Social & messaging
Follow graphs, threaded replies, and one write fanning out to millions of readers.
Photo sharing at scale — a follow graph, multi-media posts, threaded comments, hashtags and ephemeral stories.
Threaded link aggregator: subreddits own posts, comments nest into arbitrarily deep trees, and votes, awards and mod actions hang off both.
Workspace messaging with threads, channels, DMs, files, the app platform and an audit trail.
Commerce
Catalogues, carts, and orders that must not be rewritten when a price changes.
Catalogue, variants, carts, orders and payments — the schema every side project eventually becomes.
A full marketplace: many sellers listing the same product, priced and stocked per warehouse.
A food delivery marketplace in MongoDB — embedded menus and order snapshots, plus riders, payments and refunds.
Streaming
Catalogue metadata, resume points, and rights that differ by region.
Streaming end to end: billing, a title catalogue, per-region rights, encoded assets and playback telemetry.
Video at scale — channels, transcoded renditions, playlists, threaded comments, subscriptions and watch history.
Marketplaces & booking
Inventory that is only free until somebody takes it, and holds that expire.
Ride hailing — riders and drivers share one account table, trips carry both, and every fare is broken down before it is charged.
Short-stay marketplace: hosts list places, guests book dates off a per-night calendar, and both sides review each other.
Venues, showtimes and per-showtime seat inventory with expiring holds — the schema behind selling the same seat twice a day but never twice at once.
Money
Double-entry ledgers that balance, and one order filling in many pieces.
A Stripe-shaped processor: intents, charges, disputes and payouts, all posted into a double-entry ledger that has to balance.
Retail core banking — joint accounts, double-entry ledger, cards, loans and interest accrual.
A brokerage: accounts, orders that fill in pieces, positions, margin and a cash ledger that settles on T+1.
Developer tools
Recursive trees and object graphs that were never really tables.
Repositories, the git object graph, pull requests, issues and Actions — the whole code host in one diagram.
A document-database take on a workspace app — recursive blocks, embedded rich text and versioned database schemas.
A headless CMS in MongoDB: a page owns its ordered blocks, and every save writes a whole snapshot of the page rather than a diff.
Operations
Machines reporting in and people answering tickets — samples arriving in buckets, and a policy frozen at the moment it applied.
Vehicle telemetry in MongoDB, modelled the way time series has to be: readings arrive as buckets of samples, not one document per sample.
A ticketing system in MongoDB: the conversation lives inside the ticket, and the SLA it was measured against is copied in rather than looked up.
Learning MongoDB
Three small ones for the first question a document schema asks: what belongs inside the document, and what stays a collection of its own.
The smallest document schema worth reading: a note keeps its own tags and its own counters inside itself, so opening one is a single read.
Why embedding beats joining, in one picture: nobody ever asks for an ingredient without the recipe it belongs to, so the ingredients live in the recipe.
Analytics events, where every event name carries different keys — the payload is a document instead of the wide sparse table a relational schema would need.