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Thank you for writing this, I've been building a large backend with FastAPI for the last year or so and I've gone through all the levels of the purgatory. I be

Thank you for writing this, I've been building a large backend with FastAPI for the last year or so and I've gone through all the levels of the purgatory. I began using the standard "tutorial" style and started cringing when I saw the official template [1] place all CRUD operations in a single file (I've been doing Rails and Spring for a while before) and the way dependencies where managed... let's just say I wasn't feeling very comfortable. Then came the SQLModel problems. The author pushes it very hard in the FastAPI docs (which imho are terrible because when I'm looking for docs I want that, documentation, not a fancy tutorial) but as an ORM (yes I know its a layer on top of SQLAlchemy) it doesn't even support polymorphic models and the community even has contributed PRs that have gone months without any review (is it even maintained anymore? I honestly can't tell). I guess I'm the only one to blame for choosing FastAPI to build a big project but after having used it quite a lot (and also read its code because again, docs are extremely poor) I wouldn't recommend it for anything serious. Sure, if you want to build a quick CRUD then go ahead and use SQLModel and FastAPI, but keep in mind that its not built for complex applications (at least not without requiring you to write a framework on top, like I've unfortunately done). So yeah, a big thank you to the author of this post because I will migrate to Litestar as soon as I wake up tomorrow.

rmonvfer 1y ago
edit: reading the litestar docs, it even has a built-in event system! I spent a couple weeks building something I could use with FastAPI...
- sureglymop 1y ago
  Looking at the docs and trying to figure out what this is for. Is it essentially when you want to break out of the "request lifecycle" and queue something to run after your response has already been returned? It strikes me that I haven't used web frameworks a lot and never even questioned how that may not be an easy thing to do!
  - dontlaugh 1y ago
    They seem to fill the same purpose as django's signals.
miki123211 1y ago
TBH, the FastAPI "docs" are at https://github.com/polarsource/polar/tree/main/server https://github.com/polarsource/polar/tree/main/server If you want to actually figure out how to scale FastAPI for a large-ish app, including auth, testing and all that stuff, all with modern practices, "how they do it in that repo" is probably a good way to start with.
- ilumanty 1y ago
  FastAPI used to have an emoji-ridden docs page for concurrency. Criticism was not handled well. This made it clear to me that something about the project is off. https://github.com/fastapi/fastapi/discussions/6656 https://github.com/fastapi/fastapi/discussions/6656
  - stackskipton 1y ago
    Tiangolo is type who wants to do it his way without a ton of input . One of reasons Litestar was developed.
- rmonvfer 1y ago
  Thank you! I’m actually pretty happy with what I’ve built tbh and how far has FastAPI taken us but this repo is proof that you have to reinvent the wheel if you want to build something serious. In any case, that’s a treasure trove right there!, I actually had no idea Polar was open source, much less that it’s built on FastAPI! It’s such a shame that the actual documentation doesn’t even scratch the surface, I would’ve saved so much time if they just included a disclaimer along the lines of “Hey, this architecture we are showing here it’s only valid for toy projects, you will need much more work to build a real production system” but again, I guess I’m the only one to blame.
  - whilenot-dev 1y ago
    > you have to reinvent the wheel if you want to build something serious [...] guess I’m the only one to blame. The main benefit from micro frameworks like FastAPI/Flask/Express.js is that you must build your own framework! You can pick the building blocks that will make your life easier, instead of relying on choices that made the maintainer life in full-fledged frameworks like Django/Laravel/RoR bearable. Of course, you'd need to be comfortable building frameworks and doing that work additionally to the domain modeling - pick the right tool for the job and all.
no_carrier 1y ago
> Then came the SQLModel problems. The author pushes it very hard in the FastAPI docs No it doesn't? The front page for FastAPI contains a pretty lengthy tutorial with no mention of SQLModel. The only time SQLModel gets a significant mention is on a page explaining connecting a relational DB, but it makes it clear that any DB at all can be used. Something has to be chosen for the tutorial, so it makes sense the author would choose their own. If SQLModel isn't right for you then you're the only person to blame. I've been through that tutorial before and settled on plain old SQLAlchemy.
canadiantim 1y ago
Doesn't Litestar suffer from some of this too? Do you think Litestar would be better for building complex applications than FastAPI, despite less community adoption / documentation / discussion?
- croemer 1y ago
  Is there really less documentation? FastAPI mostly has tutorials to get started and is light on deep/reference material. A single person can only do so much.
  - canadiantim 1y ago
    Documentation-wise I'm mainly comparing to Django, because I agree FastAPI actually quite light on reference docs too. I've actually tried using litestar before and always been keeping an eye on it, but for a full fledged website needing forms, auth, etc. I find it hard to move away from just slightly tweaking Django for my needs - but still I feel drawn to Litestar as it's in between FastAPI and Django but still much closer to the former. I hope/believe in time I will feel comfortable migrating to Litestar for complex sites
    - ubercore 1y ago
      For forms and auth style apps, Django will probably always be the better choice.
kreelman 1y ago
I'm starting out with API style apps. This post was great since it covered several architectural and tool points I'd not thought of. I think I'll use LiteStar for my app now too. Thanks for your good comment and I 2nd your thanks to the author.

rmonvfer 1y ago

edit: reading the litestar docs, it even has a built-in event system! I spent a couple weeks building something I could use with FastAPI...

sureglymop 1y ago
Looking at the docs and trying to figure out what this is for. Is it essentially when you want to break out of the "request lifecycle" and queue something to run after your response has already been returned? It strikes me that I haven't used web frameworks a lot and never even questioned how that may not be an easy thing to do!
- dontlaugh 1y ago
  They seem to fill the same purpose as django's signals.

miki123211 1y ago

TBH, the FastAPI "docs" are at https://github.com/polarsource/polar/tree/main/server https://github.com/polarsource/polar/tree/main/server If you want to actually figure out how to scale FastAPI for a large-ish app, including auth, testing and all that stuff, all with modern practices, "how they do it in that repo" is probably a good way to start with.

ilumanty 1y ago
FastAPI used to have an emoji-ridden docs page for concurrency. Criticism was not handled well. This made it clear to me that something about the project is off. https://github.com/fastapi/fastapi/discussions/6656 https://github.com/fastapi/fastapi/discussions/6656
- stackskipton 1y ago
  Tiangolo is type who wants to do it his way without a ton of input . One of reasons Litestar was developed.
rmonvfer 1y ago
Thank you! I’m actually pretty happy with what I’ve built tbh and how far has FastAPI taken us but this repo is proof that you have to reinvent the wheel if you want to build something serious. In any case, that’s a treasure trove right there!, I actually had no idea Polar was open source, much less that it’s built on FastAPI! It’s such a shame that the actual documentation doesn’t even scratch the surface, I would’ve saved so much time if they just included a disclaimer along the lines of “Hey, this architecture we are showing here it’s only valid for toy projects, you will need much more work to build a real production system” but again, I guess I’m the only one to blame.
- whilenot-dev 1y ago
  > you have to reinvent the wheel if you want to build something serious [...] guess I’m the only one to blame. The main benefit from micro frameworks like FastAPI/Flask/Express.js is that you must build your own framework! You can pick the building blocks that will make your life easier, instead of relying on choices that made the maintainer life in full-fledged frameworks like Django/Laravel/RoR bearable. Of course, you'd need to be comfortable building frameworks and doing that work additionally to the domain modeling - pick the right tool for the job and all.

no_carrier 1y ago

> Then came the SQLModel problems. The author pushes it very hard in the FastAPI docs No it doesn't? The front page for FastAPI contains a pretty lengthy tutorial with no mention of SQLModel. The only time SQLModel gets a significant mention is on a page explaining connecting a relational DB, but it makes it clear that any DB at all can be used. Something has to be chosen for the tutorial, so it makes sense the author would choose their own. If SQLModel isn't right for you then you're the only person to blame. I've been through that tutorial before and settled on plain old SQLAlchemy.

canadiantim 1y ago

Doesn't Litestar suffer from some of this too? Do you think Litestar would be better for building complex applications than FastAPI, despite less community adoption / documentation / discussion?

croemer 1y ago
Is there really less documentation? FastAPI mostly has tutorials to get started and is light on deep/reference material. A single person can only do so much.
- canadiantim 1y ago
  Documentation-wise I'm mainly comparing to Django, because I agree FastAPI actually quite light on reference docs too. I've actually tried using litestar before and always been keeping an eye on it, but for a full fledged website needing forms, auth, etc. I find it hard to move away from just slightly tweaking Django for my needs - but still I feel drawn to Litestar as it's in between FastAPI and Django but still much closer to the former. I hope/believe in time I will feel comfortable migrating to Litestar for complex sites
  - ubercore 1y ago
    For forms and auth style apps, Django will probably always be the better choice.

kreelman 1y ago

I'm starting out with API style apps. This post was great since it covered several architectural and tool points I'd not thought of. I think I'll use LiteStar for my app now too. Thanks for your good comment and I 2nd your thanks to the author.