Doorcode
Access that expires by itself
Problem
A host gives out the door code. It never changes, so every guest since 2023 can still get in, along with their friends and whoever they told. Changing it means messaging everyone currently booked, so it never changes.
Why now
Smart locks with API access got cheap and common, and short-let regulation increasingly expects a record of who had access when.
Solution
Each booking gets its own code, live from check-in to check-out and dead after. Cleaners get their own window. The record of who could open the door, and when, exists without anyone maintaining it.
Who it is for
A short-let host with a handful of properties and a code that has not changed in two years. Changing it means messaging everyone currently booked, so it never changes, which means every guest since 2023 can still get in, along with their friends and whoever they told. Nobody decided this. It is simply what happens when changing costs an afternoon.
What you could earn from Doorcode
Say you build Doorcode and charge your own customers $29 a month, the price the score suggests. The numbers below are the revenue that would come from them. This is money you earn, never a fee you pay UpgradIQ, and we never take a cut. It is arithmetic off the price, not a promise the customers arrive on their own.
See what Doorcode produces
Each booking gets its own code, live from check-in to check-out and dead after. Cleaners get their own window. The record of who could open the door, and when, exists without anyone maintaining it.
Your build kit for Doorcode
Start the build and the kit opens two steps in, then drip-feeds the rest one phase at a time. Every phase is a copy-paste prompt for your agent with its own verification before the next unlocks, so Doorcode moves from an empty folder to a running MVP without you ever holding the whole plan in your head.
Progress saves across every device, and the workspace always reopens on the exact step you left, so a build that runs over several weeks survives them instead of dying in a browser tab you eventually close.
How you actually build it
Connect your coding agent once. It pulls the current phase straight from your kit over MCP: the exact prompt, the outcome to aim for, and the check to run before it moves on. You review and ship, it does the typing.
No copy-paste juggling, no thread to lose. The kit stays the single source of truth, and your agent works through it one phase at a time, verifying its own work at each step before the next phase is unlocked.
Take the context file, free
This is the AGENTS.md that keeps your coding agent on scope for the entire build: what Doorcode is, who it is for, the stack, the non-goals, and the rules it must follow. Copy it into your project now, no account needed, and your agent is briefed before you write a line.
# Doorcode Access that expires by itself ## What this is Each booking gets its own code, live from check-in to check-out and dead after. Cleaners get their own window. The record of who could open the door, and when, exists without anyone maintaining it. ## The problem it solves A host gives out the door code. It never changes, so every guest since 2023 can still get in, along with their friends and whoever they told. Changing it means messaging everyone currently booked, so it never changes. ## Who it is for A short-let host with a handful of properties and a code that has not changed in two years. Changing it means messaging everyone currently booked, so it never changes, which means every guest since 2023 can still get in, along with their friends and whoever they told. Nobody decided this. It is simply what happens when changing costs an afternoon. ## Stack Next.js + Postgres ## Non-goals Do not build features outside the core job above. This product exists to do one thing well. Every extra feature is a reason it does not ship. ## Rules for the agent - Build one phase at a time. Do not run ahead into later phases. - Validate input at every boundary where data enters. - Never put a permission or plan check in client code. - Ask before adding a dependency that a few lines would cover. - If something is ambiguous, say so rather than inventing a requirement. --- Context file from UpgradIQ · idea doorcode · prompts kit-v4
Then start free to get the ten-phase kit and run the first prompt.
The path to a running MVP
Foundation
Scaffold the stack, then wire the data model and sign-in. It is the skeleton Doorcode stands on, and it goes up in an evening rather than a lost week of config.
The product
Build the core feature end to end, then wire how it charges. This is where Doorcode finally turns into something that a stranger will actually pay you for.
Ship it
Test and harden, deploy it live, then open the launch-day toolkit that lands the first ten users who prove it.
Is Doorcode for you?
- You want revenue reasonably soon, not a science project
- You can give it evenings and a couple of weekends
- You can reach Short-let hosts and small landlords
- You are not ready to talk to a first real customer
- You want it fully passive, with zero maintenance
- You expect it to find its own customers without you
The 3 sections that decide whether you should actually build it, plus the full kit, are one click away.
3 more sections decide whether you build Doorcode
You have the case and the plan. Pro opens how it makes money, the one risk that kills it, and the build notes, plus the 10-phase kit that takes Doorcode to a running MVP, on this idea and all 200.
How it makes money
Main risk
Build notes
What is free here, and what Pro unlocks
Frequently asked
Is Doorcode actually validated?
It scored UIQ 78 with a GO verdict, weighed across eight sub-scores on the same rubric as every idea. GO means 75 and above, so demand and buildability were judged, not guessed.
What stack does it use?
Doorcode is built on Next.js + Postgres, chosen because a coding agent can carry most of it. You are not fighting infrastructure, you are shipping the feature that matters.
How long to a running MVP?
The kit is ten phases, drip-fed one at a time so you always know the single next step. An evening and a weekend for the lighter builds, a few focused weeks for the deeper ones.
What does the $29 a month mean?
It is the price the model suggests Doorcode could charge its own customers, not a fee to us. It is here so the money question is answered before you build, not after.
Which agent do I need?
Any capable coding agent: Claude Code, Cursor, Lovable, or Bolt. Every phase is a copy-paste prompt with its own check, so the agent does the typing and you keep the judgement.
What is free versus Pro?
The whole case above is free: the problem, timing, solution, buyer, and the full score. Pro adds how it makes money, the one risk that could kill it, and the full kit that carries Doorcode from an empty folder to a running MVP.
More like Doorcode
All 6 Property ideasBuild Doorcode, not just read about it
You have the problem, the timing, the solution and the buyer. A plan opens how it makes money, the risk that kills it, and the kit that takes it to a running MVP.
Start building Doorcode