perf: avoid cloning events in InMemoryEventStore::read_stream #363

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opened 2026-04-12 11:56:15 -07:00 by jwilger-ai-bot · 0 comments

jwilger-ai-bot commented

2026-04-12 11:56:15 -07:00

(Migrated from github.com)

Problem

InMemoryEventStore::read_stream() clones every event during reads (event.clone() at eventcore-memory/src/lib.rs:110). For 1000 events, that's 1000 heap allocations just to read state.

Benchmark: read 1000 events takes 43 µs (22M elem/sec). The cloning overhead is a portion of this.

Proposed Solution

Store events as Arc<dyn Any + Send + Sync> instead of Box<dyn Any + Send + Sync>. Reads would clone the Arc (cheap pointer increment) rather than deep-cloning the event data.

Expected Impact

Minor — estimated 43 µs → ~20 µs for reading 1000 events. The in-memory store is primarily used for testing, so this is low priority.

Caveats

The in-memory store is designed for testing and development, not production workloads. This optimization matters only if the in-memory store is used for benchmarking other components where read overhead should be minimized.

Location

eventcore-memory/src/lib.rs — storage types and read_stream() method.

Benchmark Baseline

Run cargo bench -p eventcore-bench --bench store_operations -- 'store/read_stream/memory' to measure before/after.

## Problem `InMemoryEventStore::read_stream()` clones every event during reads (`event.clone()` at `eventcore-memory/src/lib.rs:110`). For 1000 events, that's 1000 heap allocations just to read state. Benchmark: read 1000 events takes 43 µs (22M elem/sec). The cloning overhead is a portion of this. ## Proposed Solution Store events as `Arc<dyn Any + Send + Sync>` instead of `Box<dyn Any + Send + Sync>`. Reads would clone the `Arc` (cheap pointer increment) rather than deep-cloning the event data. ## Expected Impact Minor — estimated 43 µs → ~20 µs for reading 1000 events. The in-memory store is primarily used for testing, so this is low priority. ## Caveats The in-memory store is designed for testing and development, not production workloads. This optimization matters only if the in-memory store is used for benchmarking other components where read overhead should be minimized. ## Location `eventcore-memory/src/lib.rs` — storage types and `read_stream()` method. ## Benchmark Baseline Run `cargo bench -p eventcore-bench --bench store_operations -- 'store/read_stream/memory'` to measure before/after.