Hi!

I noticed that in the Cargo.toml file Link-Time Optimization (LTO) for the project is not enabled. I suggest switching it on since it will reduce the binary size (always a good thing to have) and will likely improve the application's performance. We can apply the recommended options to the cargo-lambda itself.

I think you can enable LTO only for the Release builds so as not to sacrifice the developers' experience while working on the project, since LTO consumes an additional amount of time to finish the compilation routine. In this case, we can create a dedicated [profile.optimized-dev] profile where LTO will be disabled (so developers experience will not be affected). If we enable it on the Cargo profile level for the Release profile, users, who install the application with cargo install (and in other places like existing CI scripts), will get the LTO-optimized version of the app "automatically". E.g., check cargo-outdated Release profile. You also could be interested in other optimization options like codegen-units = 1 - it also brings improvements over the current defaults.

Basically, it can be enabled with the following lines:

[profile.release]
codegen-units = 1
lto = true

I have made quick tests (AMD Ryzen 5900x, Fedora 41, Rust 1.84.1, the latest version of the project at the moment, cargo build --release command) - here are the results:

• Release (current default): 42 MiB, clean build time: 82s
• Release + codegen-units = 1 + Fat LTO: 32 MiB, clean build time: 243s

Since cargo-lambda releases not so frequently, I think we can afford this build time overhead for delivering a better user experience for all users. I specifically used Fat LTO instead of Thin LTO since it leads to better compiler optimizations.

Thank you.