Optimize Contract Compilation with LRU Caching by 3alpha · Pull Request #906 · 0xSpaceShard/starknet-devnet

3alpha · 2026-02-09T10:00:39Z

Optimize Contract Compilation with LRU Caching

Problem

Contract compilation is one of the most resource-intensive operations in Devnet. Profiling revealed that the same Sierra contract class is frequently compiled multiple times during normal blockchain interactions.

Solution

Implemented an LRU cache (max 10 entries) for compiled CASM contracts in compile_sierra_contract_json:

Uses ahash::AHasher for high-performance cache key hashing
Thread-safe via Mutex<LruCache>
Transparent to callers—no API changes required

This approach elegantly solves the performance issue without requiring invasive architectural changes to Devnet's transaction handling or fee estimation flows.

Usage related changes

Devnet speedup.

Development related changes

None.

Checklist:

Summary by CodeRabbit

Performance Improvements
- Introduced smart contract compilation caching to reduce compilation overhead and improve deployment speed. Recently compiled contracts are now automatically cached and reused, accelerating repeated operations and enhancing overall system performance.
Chores
- Added dependencies to support the new caching infrastructure.

coderabbitai · 2026-02-09T10:00:50Z

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Walkthrough

This pull request introduces caching for Sierra-to-CASM contract compilation. It adds three new dependencies (ahash, lru, parking_lot) to support fast hashing and cache management. The compilation logic in contract_class.rs is refactored to delegate to a new compile_sierra_contract_json function. A 10-entry LRU cache is implemented in utils.rs that stores compiled CASM contracts using hashed Sierra JSON input as the cache key, reducing redundant compilation work.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: implementing LRU caching to optimize contract compilation performance, which matches the core functionality changes in the PR.
Description check	✅ Passed	The PR description follows the required template structure with clear Problem/Solution sections, Usage and Development changes, and a completed checklist with all items marked done.

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✨ Finishing touches

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Commit unit tests in branch cache-casm-compilation

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3alpha · 2026-02-09T12:41:41Z

@coderabbitai review

coderabbitai · 2026-02-09T12:41:53Z

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Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/starknet-devnet-types/src/utils.rs`:
- Around line 112-118: The current cache key uses a single u64 (`cache_key`
computed from `sierra_contract_json` via `AHasher`), which risks silent
collisions; change the key to a wider representation — e.g. compute a 128-bit
key (tuple (u64,u64) from two AHasher invocations or by seeding) and make the
cache an LruCache<(u64,u64), CasmContractClass> (or use LruCache<String,
CasmContractClass> to store the full `sierra_contract_json.to_string()`), update
usages of `cache_key` and the cache type accordingly, and ensure both hashing
and cache lookup use the same new key representation so hits are verified
against the wider hash.

🧹 Nitpick comments (2)

crates/starknet-devnet-types/src/utils.rs (1)

113-118: to_string() on every call serializes the full JSON just to compute a hash.

On cache hits this serialization cost is pure overhead. Since sierra_contract_json is already a serde_json::Value, you're allocating and formatting the entire JSON tree. For large Sierra contracts this can be non-trivial.

If performance is a concern, consider hashing the serde_json::Value directly via a custom Hash impl or hashing during serialization with a Hasher-backed Write adapter, avoiding the intermediate String allocation. That said, this is still far cheaper than recompilation, so it's a reasonable trade-off for now.

crates/starknet-devnet-types/src/rpc/contract_class.rs (1)

23-27: Import paths follow inconsistent patterns: crate::compile_sierra_contract_json uses the re-export while crate::utils::compile_sierra_contract uses the direct module path.

Both imports are valid, but for consistency, either import both from crate:: (via re-exports in lib.rs) or both from crate::utils::.

crates/starknet-devnet-types/src/utils.rs

Cache compilation results

71a9963

coderabbitai bot reviewed Feb 9, 2026

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crates/starknet-devnet-types/src/utils.rs Show resolved Hide resolved

3alpha added 2 commits February 9, 2026 13:59

Add verification to avoid unlikely cache collisions

a173d48

Style changes, slight optimizations

ce41e17

3alpha merged commit 3a83832 into main Feb 10, 2026
3 checks passed

3alpha deleted the cache-casm-compilation branch February 10, 2026 06:46

3alpha added the performance label Feb 10, 2026

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Optimize Contract Compilation with LRU Caching#906

Optimize Contract Compilation with LRU Caching#906
3alpha merged 3 commits intomainfrom
cache-casm-compilation

3alpha commented Feb 9, 2026 •

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