Show HN: One prompt generates an app with its own database

manyminiapps.com

76 points by stopachka 2 days ago

Hey HN, manyminiapps is the world first massively multiplayer online mini app builder (MMOMA)

*Here’s what it does:*

You load the page. You write 1 prompt and you get a mini app back in under 2 minutes. There’s no sign up, and you can see what everyone’s creating in real-time!

Each mini app comes with it’s own database and backend, so you can build shareable apps that save data.

*What’s different*

There are a lot of app builders that promise you’ll build production software for others. But we think true production software can take a long time to get right. Even if you don’t need to program there’s a lot of work involved.

What if we turned the promise around? Instead of “you vibe code software companies”, it’s “you build fun software for yourself”.

If you cut the problem right, LLMs as they are today can already deliver personal software. manyminiapps is meant to be an experiment to demonstrate this.

You may wonder: do you really need personal software? We’re not 100% sure, but it’s definitely an interesting question. Using manyminiapps so far has been surprising! We thought our friends would just try to build the common todo app, but instead we found them building wedding planners, chord progression helpers, inspiration lists, and retro games.

*How it works*

Instead of spinning up VMs or separate instances per app, we built a multi-tenant graph database on top of 1 large Postgres instance.

All databases live under 1 table, on an EAV table (entity, attribute, value). This makes it so creating an “app” is as light as creating a new row.

If you have heard of EAV tables before, you may know that most Postgres experts will tell you not to use them. Postgres needs to know statistics in order to make efficient query plans. But when you use EAV tables, Postgres can no longer get good statistics. This is usually a bad idea.

But we thought it was worth solving to get a multi-tenant relational database. To solve this problem we started saving our own statistics in a custom table. We use count-min sketches to keep stats about each app’s columns. When a user writes a query, we figure out the indexes to use and get pg_hint_plan to tell Postgres what to do.

*What we’ve learned so far*

We’ve tried both GPT 5, Claude Opus, and Claude Sonnet for LLM providers.

GPT 5 followed the instructions the best amongst the models. Even if you told it a completely nonsensical prompt (like “absda”, it would follow the system prompt and make an app for you. But GPT 5 was also the “most lazy”. The apps that came out tended to feel too simple, with little UI detail.

Both Claude Opus and Sonnet were less good at following instructions. Even when we told them to return just the code, they wanted to returned markdown blocks. But, after parsing through those blocks, the resulting apps felt much better.

To our surprise, we didn’t notice a difference in quality from Opus and Sonnet. Both models did well, with perhaps Sonnet following instructions more closely.

To get good results we iterated on prompts. We initially tried giving point-by-point instructions, but found that a prompt with a full example tended to do better. Here’s what we landed on:

https://gist.github.com/stopachka/a6b07e1e6daeb85fa7c9555d8f...

Let us know what you think, and hope you have fun : )

jjbinx007 a day ago

Surprisingly good. I asked it to create a quiz that asks if a celebrity is alive or dead and it made this:

https://hope-rock-071r26.manyminiapps.com

It decided which celebrities to use and also sourced photos for some of them

  • stopachka a day ago

    Cool! It always surprises me how well LLMs can remember things: even full URLs are no match for it.

  • reddit_clone a day ago

    Cool. I gave it a shot. It repeated Betty White :-)

tosh 2 days ago

How are you generating the apps? Do you use an agent SDK or is it home grown?

The everything in one EAV table concept sounds very interesting as well. Can you say more about that? What kind of queries does it support? Sounds a bit like datomic or datascript. How do you tell the agent to use it?

  • stopachka a day ago

    > Can you say more about that? What kind of queries does it support? Sounds a bit like datomic or datascript. How do you tell the agent to use it?

    Yes, we definitely take inspiration from datomic and datascript, as well as Tao (Facebook's DB). EAVs have a few good properties. First, it's more natural to do last-write-wins at the column level this way. Second, we get a real shot at creating a multi-tenant database.

    With EAVs you can either query them with datalog, or use SQL CTEs. Fun fact, on Instant's backend, we use a datalog-like langauge as intermediary representation, which ends up converting to a SQL CTE.

    Technically, you can make query on these as you can on a traditional SQL DB.

    To interact with all this, users (and in proxy agents) use a graphql-like language, called InstaQL. It's like if GraphQL was represented as plain javascript objects.

    Here's the system prompt, which shows these off:

    https://gist.github.com/stopachka/a6b07e1e6daeb85fa7c9555d8f...

  • stopachka 2 days ago

    > Do you use an agent SDK or is it home grown?

    It's about 260 lines of home-grown code. Here's a snippet of how it looks:

    https://gist.github.com/stopachka/a38f00545d048661cf15a3cf4d...

    Two interesting things there:

    1. Since Instant is reactive, we use it to convey the stream to the client. This way all chats are "resumable" by default, even if the user refreshes the page.

    2. To make sure Instant writes don't block the stream, we use a "natural" buffer approach. Basically tokens from the LLM buffer up during every save.

stopachka 2 days ago

Note for folks trying to hack this :) ->

Each mini app runs on a subdomain, and the code is evaluated on the local machine. Since a few hackers are interested in the LLM details: Right now we are running Opus 4.1, but we might switch it.

Incipient a day ago

Wow people are asses on the internet. Great job making prompts public. It's pretty hilarious to see how basic and bitter some people are haha.

Cool tool however. Very coherent output given how I find AI.

One question however, if op or anyone knows, any good way/at all to feed a UI and UI interactions back into a model?

  • stopachka 18 hours ago

    > Great job making prompts public.

    Lesson learned, we just added a content moderation filter!

    > any good way/at all to feed a UI and UI interactions back into a model?

    Right now no, but it's definitely something we'd want to explore. That, and "forking" could be interesting.

apricot13 a day ago

this is incredible! I've managed to get an error in one of my attempts though. I'm on mobile so unable to look at the console, it would be great to be able to mark it as broken

an application to create a database and API of Sylvanian families and track which ones you own and want: https://lush-swan-w7nqsq.manyminiapps.com/

interesting to see that the first app I created allowed user submissions and within seconds there was a slur submitted but now that submission has been removed!

stopachka 14 hours ago

Update Sep 19:

Alas, we had to add sign in, and scope sign ins to users with an @gmail.com account.

We got a few trolls who were really motivated to use up as many tokens as possible.

We tried blocking Eastern Europe and Indonesia, but that wasn't enough. Hopefully the sign up will help alleviate this a bit.

NoSalt 2 days ago

Application error: a client-side exception has occurred while loading pure-palm-djnlwn.manyminiapps.com (see the browser console for more information).

Uncaught QueryValidationError: At path 'worlds.snapshots.$': 'limit' can only be used on top-level namespaces. It cannot be used in nested queries. NextJS 7 tP tL tq tq tV subscribeQuery subscribeQuery 122-677938205b479825.js:1:45042 NextJS 128 tP tL tq tq tV subscribeQuery subscribeQuery a av o0 ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS ux uS

  • stopachka 2 days ago

    Oh, interesting! I just took a look.

    I updated the system prompt a bit, here's a version of your app that's working with it:

    https://brave-elm-7m6ar8.manyminiapps.com/

    (The chat: https://www.manyminiapps.com/?c=1a5d3481-d2e2-414c-a7c3-4d0c...)

    ---

    For the curious, the issue was that the LLM originally decided to write the query:

    ```

        const { data } = db.useQuery({
      worlds: {
        $: { order: { createdAt: 'desc' } },
        snapshots: {
          $: { order: { timestamp: 'desc' }, limit: 1 }
        }
      }
    });
    ```

    But we don't support limits on subqueries yet.

    We had a specific note in the system prompt warning the LLM to avoid this. Interestingly, _removing_ the warning fixed the issue. I guess it's kind of like telling someone to not think of a red elephant.

    • NoSalt 18 hours ago

      Woah ... I am now 100% impressed!!! This is absolutely FANTASTIC!!!

      • stopachka 18 hours ago

        Thank you for the kind words!

throwaway0236 a day ago

I asked it to make a game where you place movies on a time line by dragging the movie poster.

Instead of the movie poster, it decided on its own to use icons that represent the movie instead (a pill represents Matrix, a gun Goodfellas etc.). I was surprised by its creativity to get around any copyright issues.

https://great-orca-9mjte9.manyminiapps.com

  • SahAssar 20 hours ago

    Doesn't seem to work for me on desktop chrome or firefox (linux), dragging the movie does nothing.

    • throwaway0236 19 hours ago

      It works for me (desktop chrome on mac). There are some glitches sometimes when the movies start spanning more than one row.

      The initial movie needs to be dragged on the thin white line (not exactly good ux). Perhaps it's not visible?

      Also, if you have dragged the first movie and place the second movie incorrectly, it will be placed back in the "stack"

  • v-yanakiev a day ago

    Doesn't seem to work on mobile (Safari).

udioron 2 days ago

wow it works https://joyful-star-ow6vuo.manyminiapps.com/

    > build a bingo board app for a group of friends. the owner  enters texts (options) in a textbox.
    > A link is generated that can be sent to participants.
    > They enter their name and can can mark bingo options (5x5 with joker at center) and see a scoreboard.
  • serial_dev 2 days ago

    I got this with a very short and basic prompt, it lets the user track blood sugar and ketone levels.

    It worked really well, and it was very fast, especially considering that it is on the front page of HN. Congrats, very cool project

    Link to the app https://vital-crow-mmrs4s.manyminiapps.com/

sladix a day ago

You probably want a first moderation layer before triggering the whole process

  • stopachka 18 hours ago

    Just added this, thank you. It's interesting how the trolls were quiet effectively between 8AM - 9PM yesterday. They really do look to work at night.

ch4s3 2 days ago

Some of there are pretty cools, trying to see if it can run a multiplayer doom.

  • stopachka 2 days ago

    Oo cool idea! We don't limit the input size, so you could add more context. I wonder if giving it some docs on Instant's presence [1] could help it do the right thing with Doom. Ideally movements should be ephemeral rather than stored in the DB, and the system prompt we have doesn't say too much about that.

    [1] https://www.instantdb.com/docs/presence-and-topics.md

    • ch4s3 2 days ago

      Here's my prompt

      >Build a simple lofi black and white multiplayer doom clone where players drop in near each other in a procedural generated forest world. The graphics should be 2d in a 3d world. Players enter their name before joining. The DB tracks players names, scores, deaths, total play time. When a players is shot too many times and dies they randomly respawn. Players should spawn within visual range of each other. add some harmless non-players animals that roam around. generate some forest background noise to play. players should make a little sound when they walk that other players can hear. players should be able to hide behind trees. Try to make it fun.

      It basically worked. https://www.manyminiapps.com/?c=da20213e-6832-4cd8-ac73-7669...

    • ch4s3 a day ago

      Thanks again! This really gave me the familiar old feeling of finding something delightful online.

dawnerd a day ago

https://happy-oak-1pe974.manyminiapps.com

tried to recreate itself

  • stopachka a day ago

    Nice! I liked it's creativity in there. Since it doesn't haven LLM to generate code, it just writes a basic boilerplate and inserts your prompt.

    Ah, wish there was a way it had access to babel/runtime. [1]

    [1] Though then the mini app builder inside the mini app builder would have a security vulernability, if the mini mini apps actually evaluated.

stopachka 2 days ago

Update: Claude just went down. We are switching to GPT 5 right now. Will update as soon as we're deployed.

  • stopachka 2 days ago

    Update 2: Claude seems to be back. We have the GPT 5 version ready, just in case now : )

rjh29 2 days ago

I tried a few random apps but the UI section was blank white...

  • stopachka 2 days ago

    Oh that's weird. Would you mind sending over a few links of the apps you made?

cognomano a day ago

We are not in Kansas anymore.

Well done.

ramesh31 2 days ago

>You load the page. You write 1 prompt and you get a mini app back in under 2 minutes.

Then what?

  • stopachka 2 days ago

    I would suggest sharing the app you built, and seeing what others come up with.

    Technically you could use the apps for yourself too, though everything is public so be wary.

  • normie3000 2 days ago

    Clicking "make" takes me straight back to the first page.

    • stopachka a day ago

      Are you still seeing this issue? I am not able to repro. If you could give me a few steps I can take can try to fix the bug

  • sunrunner 2 days ago

    Easy.

    Step 2. Scale unicorn SaaS to $1B valuation

    Step 3. Sell it, become rich, buy superyacht