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Prove your Rust skills

Rust experience is hard to judge from a CV because so much of the skill is invisible: knowing why the compiler objects and what to change. Lemma records that reasoning in live sessions and adaptive assessments.

How Rust is assessed

What Rust competence looks like

A competent Rust developer reads compiler errors as design feedback. When the borrow checker objects, they restructure ownership instead of cloning everything or reaching for unsafe. They model state with enums so invalid states cannot be represented, and they use Result and the question mark operator to keep error paths explicit.

They know the cost of their abstractions. They choose between Box, Rc and Arc deliberately, understand when trait objects or generics fit, and can explain what an async runtime is doing. Unsafe code, when it appears, is small, documented and wrapped in a safe interface with tests around it.

Rust session
Live · 41:07

Resolving a borrow checker error live

60 min · Learning · with Bruno H.

src/cache.rs Nina S. is sharing
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Bruno H. rated the session

Practitioner · after the call

Clear reasoning on ownership and borrowing. Talked through trade-offs first.

Added to RustAdded to record

Ownership and borrowing

Moving, borrowing and lifetimes, and restructuring code when the borrow checker rejects it.

Traits and generics

Defining traits, using trait bounds and choosing between static dispatch and trait objects.

Error handling

Result, Option, custom error types and propagating errors without hiding their cause.

Enums and pattern matching

Modelling state so invalid combinations do not compile, with exhaustive matches.

Async Rust

Futures, async runtimes, Send and Sync bounds, and avoiding blocking inside async tasks.

Unsafe and FFI

Keeping unsafe blocks minimal, upholding invariants and wrapping them in safe APIs.

What counts as evidence of Rust skills?

A line on a CV saying Rust is a claim. A reviewed session, an assessed level or a repository linked from your account is evidence. These are the kinds Lemma records against your Rust skill, each with where it came from. See the evidence methodology for how each source is weighed.

Skills Passport
Signed
64

Rust

Jordan L. · SCI recomputed 9 Oct

Evidence · 4 entries

  1. Resolving a borrow checker error live

    Live session · 9 Oct

    Rated 5.0

  2. Rust scenario questions

    Adaptive assessment · 2 Oct

    Level 7.2

  3. A crate or project on GitHub

    GitHub connector · 24 Sep

    Verified

  4. Ownership practice drills

    AI tutor practice · 11 Sep

    Practice
Signature valid · checked today Share link
Live session

Resolving a borrow checker error live

A practitioner hands you code that will not compile and watches you restructure it. Your explanation of why the compiler objected matters as much as the fix, and they rate both.

Adaptive assessment

Rust scenario questions

Adaptive multiple-choice questions cover ownership, lifetimes and trait behaviour. Some show code the compiler rejects and ask you to pick the correct fix. Harder questions count for more.

GitHub connector

A crate or project on GitHub

Connect a repository or commit for a crate, a CLI or a service you wrote in Rust. Lemma confirms the repository exists and your account has access to it.

AI tutor practice

Ownership practice drills

Short AI tutor exercises on moves, borrows and lifetimes build fluency. They are practice evidence, so they add a small, capped amount rather than standing in for proof.

How is a Rust skills test run on Lemma?

The Rust test runs 15 to 25 questions and adjusts difficulty to your answers, with scenarios from services under real load. The result counts alongside sessions and linked repositories toward your Rust SCI, which favours recent evidence over old.

How the SCI score is calculatedHow adaptive skills assessments workPractise Rust in live skill swap sessionsWhich evidence types countWhat your Skills Passport shows
Rust assessment
0:42
Question 11Stops when your level holds
Difficulty7/10

The compiler rejects pushing to a Vec while you hold a reference to its first element. Why?

  1. AVec is not Send
  2. BA mutable borrow overlaps a live shared one
  3. CThe element type is missing Copy
  4. Dpush needs an explicit lifetime
Locks on submit

  1. Build fluency with drills

    The AI tutor gives you ownership, trait and error-handling exercises that get harder as you improve. It rejects repeated answers and rushed submissions, and its results stay a small, capped part of your score.

  2. Work through code with a peer

    In a live session, refactor or review Rust with a practitioner. They see how you respond to compiler errors and rate the session, which is recorded as evidence for Rust.

  3. Take the Rust assessment

    Answer adaptive scenario questions, some asking why a snippet will not compile. Harder ones count for more. You cannot go back to change answers, and each question has its own time limit.

Rust skills: common questions

How do I show I can write production Rust and not just pass tutorials?

Production Rust shows up in decisions: how you model errors, structure ownership across modules and handle async. Discuss a real project in a live session so a practitioner can probe those decisions, connect the repository, and pass the adaptive assessment. That combination says more than a list of finished tutorials.

What Rust concepts do assessments focus on?

Ownership, borrowing and lifetimes come first, because most Rust bugs and compile errors trace back to them. Questions also cover traits and generics, error handling with Result, pattern matching and async behaviour. Some questions show a snippet and ask you to choose the change that makes it compile and behave correctly.

Is Rust evidence useful if most jobs ask for another language?

Yes. Rust evidence signals that you think carefully about memory, concurrency and correctness, which transfers to systems work in Go, C++ or backend services. On your Passport it sits alongside your other skills, so a hiring team sees it as depth rather than a replacement.

Can I use open source Rust contributions as proof?

You can connect a specific GitHub commit as well as a whole repository, so a merged contribution to someone else's crate counts. Lemma checks the commit exists and your account has access. External proofs are capped, so pair them with sessions and an assessment for a complete record.

Skills related to Rust

Browse the skills directory

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Evidence for system design

Go

Prove you write clear, concurrent Go services, with evidence from live code and connected repositories.

Evidence for Go

Cybersecurity

Evidence of how you find, prioritise and fix real security risks in systems and code.

Evidence for cybersecurity

Blockchain development

Evidence of how you design, test and secure smart contracts, judged by practitioners in live sessions.

Evidence for blockchain development

Start your Rust evidence record.

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