Host: What would your pitch be on why it's worth checking out Rust or working with Rust?

Alice Ryhl: You need a language that's reliable that's going to have as few bugs as possible. That's the idea of Rust.

Host: Rust is quietly spreading as a language of choice to build reliable and performant applications. But what makes it different? Alice Ryhl is a software engineer working on Google's Android Rust team, a core maintainer of Tokio, the de facto async runtime for Rust, and is a Rust language team adviser. In today's conversation, we cover the pitch on why Rust is worth to consider whether you're using TypeScript or C++ today. how concepts like ownership, the borrow checker, and the unsafe keyword work, and what are things that trip up newcomers to Rust, how the language is governed without a benevolent dictator, and how RFC's and additions work, and many more. If you want to understand what makes Rust different and why so many engineers say once it compiles, it works, this episode is for you.

Host: Alice, welcome to the podcast. It's really nice to have you here. How did you get into software engineering?

Alice Ryhl: It actually all started with Minecraft. I wanted to write my own mod for Minecraft, so I learned Java. I didn't get very far with the Minecraft modding, but that's where it started.

Host: How did you continue? Did you go to university?

Alice Ryhl: This was just before I started in high school. And then after high school, I had a year where I worked full-time as a software engineer. And then I moved on to starting my bachelor. Did that for 3 years and then I did a masters for 2 years.

Host: How did you end up at Google? Was that straight out of university?

Alice Ryhl: Actually started part-time at the same time as when I started my masters and then I switched to full-time after I finished.

Host: How did you get involved with the Rust community? Was was it at Google? Was it before Google?

Alice Ryhl: Oh, way before. I've been doing Rust for a long time. When I was in school, I spent a lot of time on the what's called the Rust users forum. Well, I was answering questions really. I have maybe 10,000 posts on there or something. At some point, I also started being active in some chat servers, the Discord server for something called Tokyo. I kept doing that, answering questions. When I saw common questions, I would fix the documentation. That's how I got into Tokyo, which I'm now one of the maintainers of.

Host: And then for those of us not as familiar with Rust and and Tokyo, what is Tokyo inside of Rust and why is it important?

Alice Ryhl: So Tokyo is well, it's an asynchronous runtime for Rust. You can think of it as the standard library for Rust when you're using async. I mean, if you compare with something like JavaScript in the browser, you might compare Tokyo with the browser itself. For example, in JavaScript, you have this loop, this event loop which has all the tasks that are able to run and then they get executed one after the other. And especially if you use the await stuff, then you can have tasks pause and then another task start running on the same thread. And Tokyo does something similar. It has a queue of things that are able to run and then it will run them. So unlike JavaScript, Tokyo can be multi-threaded. So you can have multiple cues running in parallel.

Host: This seems like a pretty core part of of Rust as a language, as a as a ecosystem. How did you gravitate towards this?

Alice Ryhl: I think part of what I liked about Rust is this feeling that as you write the code when it compiles it works. I mean this has to be in quotes right because obviously it's possible that there are bugs but this is something a lot of people say about Rust and there's a reason people say it even though it's not necessarily literally true.

Host: How do some other languages compare to begin with?

Alice Ryhl: I think to have a language that feels this way you have to have a type system. That's where it all starts. Yeah, I do think that even compared to other languages with type systems, I think Rust does a better job than many languages, even others with type systems. I mean, the the classic example is Java's null. It was Tony hair who invented the null and he called it his billiond dollar mistake because it's so easy to have I mean every time you call a function you might have a crash in your program and in Rust I think they're really good at making sure that when you call a function there's no chance that it might be null right that problem just doesn't exist so you can't have that kind of crash.

Host: and so you have to explicitly say this object might be null?

Alice Ryhl: and so you have to explicitly say this object might be null and then the compiler will force you to check for null before you use it. So you can't forget like you can in Java.

Host: Can we talk about Rust as a whole? This was a language that was created in in 20 years ago in 2006 and it feels like it's become a lot more popular over time. Do you know of like the scale that Rust is at in terms of usage or popularity or or things that among the Rust Rust community numbers that are known there?

Alice Ryhl: One thing I found kind of funny, I I checked here all the the day and uh we have actually overtaken PHP and Go on the Tyobi index.

Host: Wow. Cuz the feeling I have again in general is that Rust is popping up in more and more places. More companies are building on Rust. Oxide is a good example. they decided to go all in on Rust and like there's a sense of of Rust is is becoming a popular place to build I guess high performance applications even increasingly contributing to to the kernel as an engineer who you know might know other languages from like Typescript Java etc. What would your pitch be on why it's worth checking out Rust or working with Rust?

Alice Ryhl: That depends a lot on which language you're coming from.

Host: Oh, let's come from Typescript.

Alice Ryhl: The pit from TypeScript would be a lot different than the pit from C++. But okay, so to begin with, I think when it comes to TypeScript, Rust fits in as the backend language. That's where I would put it. I wouldn't use it in the front end. I think it's a pretty good fit for backends, API servers. One way to put it is you don't want to be waking off at night because there are problems with your web server. You need a language that's reliable, that's going to have as few bucks as possible. I mean, obviously, it would be nice if it had zero bucks, but you know, it's going to be hard to get there, but as few bucks as possible. That's the idea of Rust. I mean, I already mentioned null, but it does a lot of stuff like that. So there's no null checking and and this is done through you know it has this enum type.

Alice Ryhl: the other thing I think is quite good is uh error handling. So on one hand Russ doesn't really use exceptions. So it actually returns the error as a value. So you return a value that's either using an enum either the result or the error. And the way this is done is that there's an operator question mark which says so you write my function and then question mark at the end. And this means if this function fails return the error. So it's really easy to handle errors but it's not zero characters like like it is with exceptions right? So it's explicit on the other hand and if you forget to put the question mark that's a combination error.

Host: Another thing I quite like is how it handles documentation.

Alice Ryhl: how it handles documentation. How does it for one when you have a comment you make it into a documentation comment by having three slashes instead of two. Now the thing is you can of course write examples in your documentation and Rust makes all examples into tests. This means that if you change the underlying code now your test fails. And so this means that you can't even you can't forget to update your examples in your documentation. ... Yeah. So there's a pretty cool library called Surya (Serde) in Rust where you you have your strct so your type you know with fields and then you can say I want to be able to pass this from for example JSON and then SA will it's a macro it will generate code which checks the JSON that it's in the same format it has all the fields you need and they have the right types and it generates native code that's specific to that particular shape of JSON. So the charge are really efficient.

Host: and there's this thing which again I I learned just very recently thanks to thanks to you as we're talking ahead of this is the switch statement right so in almost every language you have a you have a switch for an enum and you handle cases and then you might have a default or you know everything else and sometimes you forget one of them.

Alice Ryhl: that's right so in rust it's not called pitch it's called match but it's the same idea you can match on your enum and then you can have a branch for each possibility at rank B and if you are missing one that's a compiler error of course you can have a catch all case if you want to but most of the time you would just list all the cases and then in the future when you add a new variant the compiler will tell you oh you need to update your code here here and here and I think this is kind of leads to another way that Rust really helps with reliability, which is that if you're refactoring, I think Rust is really good at telling you all the places you need to update. I've done this sometimes where I would refactor something. I change the code. I change the return type or whatever it is, and then I just fix the compiler errors and until the compiler stops shouting.

Host: What about the pitch from C++?

Alice Ryhl: So, here I actually think it's even stronger. The thing with C++ is that if you make a mistake, right, in in JavaScript, maybe you take down your server, which is already bad enough, but in C++ when you make a mistake there, now it's actually a security vulnerability most of the time. If you do something as trivial as you did an off by one in your IRA or whatever it might be, that's a security vulnerability and that this just keeps happening.

Host: Let's talk about memory safety.

Alice Ryhl: Memory safety is this idea that no matter how stupid the code you write is, it's not going to have a certain class of bugs. And this is the, you know, the kind of bug that usually leads into security vulnerabilities. You know, the kind of thing where you read past the array and you just look at random memory or you destroyed an object and then you used it afterwards. ... let's say you have some object and it has a field called user ID. And it's pretty common for code to write zero zeros to memory. But if you write a zero to the user ID, now you're root. ... Once you're rooe, you're lost.

Host: Why is it a good or a bad thing to have a garbage collector? Java has a garbage collector. C# has a garbage collector.

Alice Ryhl: So, a garbage collector says once you've done using your objects, there's going to be a little piece of code that checks all of your co your objects and says this is not used anymore and then it cleans it up. Whereas in languages like Rust or C++, the variable is cleaned up at the end of the scope when it goes out of scope. ... For embedded use cases, this might simply be not possible or unacceptable. ... Even for back end, it can be a problem because if you have a request incoming right when it checks all of your objects like you have some sort of latency spike.

Host: One thing I've read is on forums people complaining about fighting so-called fighting the borrow checker. What can make it challenging? ... Rust's ownership model. What what is the ownership model?

Alice Ryhl: The ownership is just the idea that if you have a variable containing some object then the object is only there. It's kind of exclusive. So for example, if you have a variable let A equals your string or whatever and then you do let B equal to A, then this is a move. And so this means that using A afterwards is now a compiler error because its contents have been moved away. And of course this is important when we don't have a garbage collector because then when B goes out of scope, it has to clean up the string. Now if A was also valid then when they both went out of scope it would clean up the string twice which is not legal.

Alice Ryhl: another pointer type we have in Rust is called the reference. ... creating a reference is called borrowing. ... the borrow checkout checks that the reference is like the last use of the reference is before the object goes out of scope. ... So you can only have one writer at a time or you can have any number of readers. It checks that on the scope like in a function.

Host: we talked about memory safety, but there is a keyword in in Rust called unsafe. What does this do and in what cases do people typically use?

Alice Ryhl: the what is unsafe is the escape hatch essentially. ... What Rust ensures is that if you have no use of unsafe, then no matter how stupid your code is, you will never have one of those bugs. ... generally when unsafe is used, it's to add a new feature to the language. ... As long as you design your API right, you can add new language features by using unsafe. The other classic example would be to call into a C library.

Host: Can we talk about how the language is is built? Who builds Rust? ... one interesting difference compared to some other popular languages like like Python or projects like like Linux is they have a benevolent dictator for life and Rust does not.

Alice Ryhl: today there's the rust project which has a bunch of different teams. ... Honestly, if the team doesn't sign off on it, it doesn't happen. ... The RFC request for comment is the way the ROS project makes big decisions but you know big ones is important to say. ...motivation, guide level explanation, reference level explanation.

Host: Can we talk a little bit about Rust in the Linux kernel on on how that has evolved?

Alice Ryhl: The the the most recent Linux plumbers from December 2025 was there. The big news were that at the Linux kernel maintainer summit, we agreed that Rust is no longer experimental in the kernel. That was really big for us compared to the previous year.

Host: Do you use any of the AI tools for your day-to-day work building Tokyo, uh contribute contributing to Rust projects?

Alice Ryhl: So, I have been trying to use them. Honestly, I'm still learning how to use these tools, but I have used them. I I quite like the Gemini command line interface. ... Rust could be a pretty promising candidate for to use for agents because they can get more feedback and it's just hard it's harder to to ship certain type of bugs. ... I have actually written a few patches with AI myself. ... saved me time if nothing else.

Host: for a senior engineer who would like to learn Rust or you know just build with it what would your suggestion to be to get started.

Alice Ryhl: the Rust book which is so it's on the official Rust website is actually really good. ... honestly the way you learn a language is you have you have a project. You you implement some sort of project with it. I mean maybe some sort of web server or something. ... John Ganget (Jon Gjengset) has another book that I think is really good and this book is kind of aimed at the intermediate Rust developer. ... there's this thing called rustlings and the idea is that they give you some unfinished rust code and your task is to finish it.

Host: Awesome, Alice. Thank you. Thank you. Thank you so much for this. This was really interesting and I've learned a bunch.

Alice Ryhl: Thank you for having me on. I hope you enjoyed getting into the details about Russ as much as I did.