Changelog and Version History

Relevant source files

The following files were used as context for generating this wiki page:

• CHANGELOG.md
• CONTRIBUTING.md
• pyproject.toml
• fastlimit/limiter.py
• fastlimit/init.py
• tests/test_edge_cases.py

Introduction

The Changelog and Version History of the FastLimit project serves as the definitive record of all notable changes, improvements, and bug fixes across the library's lifecycle. It follows the Keep a Changelog format and strictly adheres to Semantic Versioning (SemVer) to ensure predictable dependency management for developers.

This system is integrated into the development workflow through tools like commitizen, which automates version bumping and changelog generation based on conventional commits. This ensures that every release—whether it introduces new algorithms, performance optimizations, or critical security fixes—is documented with technical precision.
Sources: CHANGELOG.md:5-7, pyproject.toml:94-101, CONTRIBUTING.md:387-399

Versioning Policy

FastLimit uses the MAJOR.MINOR.PATCH format to communicate the nature of changes in each release.

Level	Description
MAJOR	Breaking changes that require updates to existing integrations.
MINOR	New features added in a backward-compatible manner.
PATCH	Backward-compatible bug fixes and internal improvements.

Sources: CONTRIBUTING.md:468-479

Automated Release Workflow

The project utilizes commitizen for managing versioning. This tool automates the following:

• Bumping versions in fastlimit/__init__.py and pyproject.toml.
• Updating the CHANGELOG.md incrementally.
• Creating Git tags using the v$version format.

Sources: pyproject.toml:94-101

Significant Release History

v0.2.0 (2026-01-24)

This release focused on API robustness and performance optimizations.

• New Features: Integrated commitizen for semantic versioning automation.
• API Improvements:
  • Made reset() and get_usage() algorithm-aware to handle different storage structures (e.g., Token Bucket vs. Sliding Window).
  • Introduced CheckResult and the check_with_info() method to eliminate redundant Redis calls when retrieving usage data for headers.
• Bug Fixes:
  • Sliding Window: Corrected inverted usage formulas and transitioned to integer-only arithmetic for higher precision.
  • Token Bucket: Implemented millisecond precision for refills to prevent crashes at low rates (e.g., 1 request/hour).
  • Fixed Window: Aligned boundaries to epochs and implemented EXPIREAT for stricter window resets.
  • Distributed Systems: Added support for Redis TIME methods to ensure consistent window boundaries across multiple application instances.

Sources: CHANGELOG.md:18-35, tests/test_edge_cases.py:176-218, fastlimit/limiter.py:165-171

v0.1.0 (2025-01-18)

The initial release established the core architecture and high-performance rate limiting capabilities.

• Core Algorithms: Implementation of Token Bucket and Sliding Window.
• Integration: FastAPI support via @limiter.limit() and RateLimitHeadersMiddleware.
• Reliability: Comprehensive exception handling (e.g., RateLimitExceeded, BackendError) and Prometheus metrics integration.
• Infrastructure: Async-first design and Docker Compose for development environments.

Sources: CHANGELOG.md:9-16, fastlimit/init.py:1-25

Release and Contribution Lifecycle

The following diagram illustrates the workflow from making a change to it appearing in the version history.

The release process ensures that all changes are verified and documented before being published.
Sources: CONTRIBUTING.md:417-434, pyproject.toml:97-101

Changelog Format Standards

To maintain clarity for downstream developers, the CHANGELOG.md categorizes changes into specific headers.

Header	Usage
Added	For new features and capabilities.
Changed	For changes in existing functionality.
Deprecated	For soon-to-be-removed features.
Removed	For features removed in the current release.
Fixed	For any bug fixes.
Security	In case of vulnerabilities or security-related improvements.

Sources: CONTRIBUTING.md:481-502

Conclusion

The changelog and versioning system in FastLimit provide a transparent and technically rigorous history of the project's evolution. By combining Semantic Versioning with automated tooling and the "Keep a Changelog" standard, the project ensures that developers can safely update the library while staying informed about critical architectural shifts and bug fixes.
Sources: CHANGELOG.md:1-7, CONTRIBUTING.md:468-471