---
title: "The Life-Changing Magic of Tidying Ruby Object Allocations"
description: "The post presents object-allocation profiling as a way to find Ruby performance hotspots, including code inside libraries such as Active Record. It uses memory_profiler and derailed_benchmarks to group allocations by gem, file, and source location, then examines whether each allocation can be removed or avoided. A benchmark compares a direct maximum comparison with an array-based version: the array allocation makes the latter 2.04x slower in the reported run. One optimization for cache_version reuses a raw database timestamp string when it is safe, checking its type, format, timezone, and provenance before deleting separators and padding PostgreSQL-truncated values. This change reduces allocation from 743,842 bytes and 6,626 objects to 702,955 bytes and 6,063 objects, and the post reports up to 1.12x faster; combined optimizations reach 1.23x overall."
---

# The Life-Changing Magic of Tidying Ruby Object Allocations

[Heroku](https://yomu.fyi/company/heroku) · Richard Schneeman · Sep 16, 2020

**Type:** Explainer

## Summary

The post presents object-allocation profiling as a way to find Ruby performance hotspots, including code inside libraries such as Active Record. It uses memory\_profiler and derailed\_benchmarks to group allocations by gem, file, and source location, then examines whether each allocation can be removed or avoided. A benchmark compares a direct maximum comparison with an array-based version: the array allocation makes the latter 2.04x slower in the reported run. One optimization for cache\_version reuses a raw database timestamp string when it is safe, checking its type, format, timezone, and provenance before deleting separators and padding PostgreSQL-truncated values. This change reduces allocation from 743,842 bytes and 6,626 objects to 702,955 bytes and 6,063 objects, and the post reports up to 1.12x faster; combined optimizations reach 1.23x overall.

## Context

The work addresses slow applications by focusing on memory allocations as a source of performance hotspots. The examples use a real-world application and include allocations originating in Rails libraries.

## Approach / What changed

The post uses memory\_profiler and derailed\_benchmarks to identify allocation hotspots by file and line, then benchmarks and refactors code to avoid unnecessary objects. One change conditionally transforms a raw database timestamp string in place for fast cache-version generation.

## Takeaways

- The reported array-allocation benchmark is 2.04x slower than a direct comparison of two values.
- The cache\_version fast path requires a String timestamp, :usec formatting, UTC timezone, and a value that did not come from the user.
- The cache\_version change cuts allocation by 40,887 bytes and 563 objects, while the post reports up to 1.12x faster performance; combined optimizations reach 1.23x.

**Tags:** [Performance](https://yomu.fyi/topic/performance), [Ruby](https://yomu.fyi/topic/ruby), [Ruby on Rails](https://yomu.fyi/topic/ruby-on-rails)

- Source: [Heroku](https://www.heroku.com/blog/tidying-ruby-object-allocations)
- Source URL: https://www.heroku.com/blog/tidying-ruby-object-allocations
- Ingested by Yomu: 2026-09-09T20:02:18.646Z

[Read original post](https://www.heroku.com/blog/tidying-ruby-object-allocations)