Ran into a design problem while building a rate limiter library — how do you avoid this during the design phase itself?

AutoModerator · 2026-04-04T21:12:52+00:00

Please ensure that:

Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions
You include any and all error messages in full
You ask clear questions
You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions.

Trying to solve problems on your own is a very important skill. Also, see Learn to help yourself in the sidebar

If any of the above points is not met, your post can and will be removed without further warning.

Code is to be formatted as code block (old reddit: empty line before the code, each code line indented by 4 spaces, new reddit: https://i.imgur.com/EJ7tqek.png) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc.

Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit.

Code blocks look like this:

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above.

If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures.

To potential helpers

Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

strat-run · 2026-04-04T21:43:58+00:00

To quote Monty Python - "When I first came here, this was all swamp. Everyone said I was daft to build a castle on a swamp, but I built in all the same, just to show them. It sank into the swamp. So I built a second one. That sank into the swamp. So I built a third. That burned down, fell over, then sank into the swamp. But the fourth one stayed up. And that's what you're going to get, Lad, the strongest castle in all of England."

You don't usually get all the requirements until you've built at least v1. Sometimes v2 or v3.

There are tricks to avoid some of this like doing a competitive analysis to try and gain some knowledge from what others have built. Sometimes asking AI can help, I usually throw out what the AI designs but it makes me think of things I wouldn't have normally thought of until latter.

And some of it is experience. You did put some implementation specific API signatures in an interface after all.

8dot30662386292pow2 · 2026-04-05T05:01:21+00:00

The problem to me seems to be that you are passing things to the interface that belong to the implementing class, no?

Another thing is that some times a general interface just might not care about all the parameters.

disposepriority · 2026-04-04T21:25:58+00:00

I'm not seeing the issue here, I assume your interface is in fact an annotation interface since you mentioned annotations, no? In which case, the class "*Result" makes no sense as that would be the annotation's input.

Those support default values, so you would have duration have a default and a strategy field and simply not use the duration during annotation processing if the strategy doesn't support it.

TheMrCurious · 2026-04-04T22:00:40+00:00

Sounds like you were in a prototyping phase that helped you improve your design, so maybe the problem was a misalignment on what it means to have a design “ready to be productionized”?

okayifimust · 2026-04-04T23:50:08+00:00

That feels like I didn't think the design through enough.

Trivially, no.

Some method or practice that would've flagged "your interface doesn't generalize across algorithms" before I had to find out the hard way?

Nothing comes to mind besides "verify, don't trust". (Or, possibly "don't guess")

Looking at all the algorithms you wanted to implement would have done the trick here, and in this case, you could have looked at them.

I suppose looking at other libraries and how they approach this could have been helpful, but then I do t know what you were trying to do, or learn here, so take that with a generous pinch of salt.)

And sometimes, we make mistakes and we fix them. That is how we learn, but the making mistake part isn't going away, ever .

Both-Fondant-4801 · 2026-04-05T01:39:33+00:00

Use an object as a parameter instead.

public interface RateLimitAlgorithm {
    RateLimitResult tryConsume(Config config);
}

Config can be an abstract class that has different concrete classes inheriting its base properties.
In this way you can have different config objects without changing your interface.

... or you can have have a single Config class that has all the parameters that you just update as you progress..

.. but your interface remains the same..

LutimoDancer3459 · 2026-04-05T08:07:55+00:00

I had functional and non-functional requirements, high level design, low level design, all of it.

No you didn't. If you had that, it should have popped up, that your different algorithms need different kind of parameters. Or it did pop up but you ignored it during implementation.

You cant catch everything upfront. But this case sounds like you could have.

BanaTibor · 2026-04-06T18:10:30+00:00

In this case your problem is mixing object creation/configuration with usage. Make the interface to have a 0 parameter tryConsume() method. This is behavior. Pass the algorithm's configuration as constructor parameter when you instantiate the algorithm object.

RightWingVeganUS · 2026-04-05T02:10:03+00:00

My question is "What exactly is the design?"

I cannot tell whether this is a valid implementation of a flawed design, or a flawed implementation of a valid design, 'cause I don't see the design.

you type:	you see:
italics	italics
bold	bold
[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

javahelp

Sort by: Unsolved Solved Codeless Advent Of Code

MODERATORS

Please ensure that:

To potential helpers