flint-limiter 0.1.0

Embedded persistent rate limiting for Python, powered by Rust

Flint

Persistent rate limiting, embedded first.

No Redis. No daemon. No broker.

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Why Flint

I was tired of adding Redis just to rate limit a local Python service.

Most rate limiters are either in-memory and reset on restart, tied to HTTP proxies, or require a separate infrastructure service. Flint embeds inside the Python process and persists counter state to a local append-only log.

The result is simple:

Python process + .flint/ directory = durable rate limiting

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What Flint Does

Flint is an embedded rate limiter with:

• Rust core;
• Python bindings via PyO3;
• append-only AOF persistence;
• single-writer data directory locking;
• GIL-aware Python API;
• CLI inspect/admin commands;
• token bucket algorithm;
• sliding window log algorithm;
• fixed window counter algorithm;
• crash recovery from local files;
• no Redis, daemon, broker, or cloud dependency.

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Comparison

Solution	Persistent	No Redis	Embedded	Observable
Flint	Yes	Yes	Yes	Yes
SlowAPI	No	Yes	Yes	No
redis-py + limits	No	No	No	No
nginx rate limit	No	Yes	No	No

Flint's unique advantage is the combination of persistent counters and zero external infrastructure.

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Install

pip install flint-limiter

The Python module is:

import flint

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Quickstart

import flint

limiter = flint.Limiter(data_dir=".flint")

limiter.limit(
    "api:user-42",
    rate=100,
    per="1m",
    algorithm="token_bucket",
)

if limiter.allow("api:user-42"):
    process_request()

With context:

result = limiter.check("api:user-42")

print(result.allowed)
print(result.remaining)
print(result.reset_at)

---

CLI

flint limit add "api:user-42" --rate 100 --per 1m --algorithm token_bucket
flint limit list
flint limit status "api:user-42"
flint limit reset "api:user-42"
flint limit history "api:user-42"

Use a custom data directory:

flint --data-dir /var/lib/myapp/flint limit status "api:user-42"

---

Algorithms

Algorithm	Use case
token_bucket	Smooth rate limiting with bursts
sliding_window_log	Precise rolling-window limits
fixed_window_counter	Simple high-throughput window counters

---

Storage

Flint stores state under data_dir:

.flint/
  flint.aof
  flint.lock

The AOF records durable events:

LIMIT_CONFIGURED
ALLOW
DENY
RESET

On restart, Flint replays the log and restores counters. A crash-truncated final line is ignored deterministically; corruption in the middle of the log fails loudly.

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What Flint Replaces

Flint replaces:

• Redis-backed rate limiting libraries;
• in-memory Python limiters that reset on restart;
• nginx-only HTTP rate limiting;
• custom database counters;
• hand-written local counters with no history.

The unique property is persistent rate limiting without Redis.

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Build And Test

cargo fmt --check
cargo clippy --workspace --all-targets -- -D warnings
cargo test --workspace

Python:

python3 -m venv .venv
.venv/bin/pip install -U pip maturin pytest
.venv/bin/maturin develop
.venv/bin/python -m pytest -q tests/python

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License

BSD 3-Clause.