Neuron

A very light php framework. Will probably not help you much.

Rate limiting

Neuron\RateLimit\RateLimiter is a fixed-window counter with weighted attempts. The cap check happens inside one conditional UPDATE, so bursts serialise on the row lock and a refused attempt never consumes budget.

use Neuron\RateLimit\DatabaseStore;
use Neuron\RateLimit\RateLimiter;

$limiter = new RateLimiter (new DatabaseStore ());          // table neuron_rate_limits
if (!$limiter->attempt ('user:export:' . $userId, 100, 3600, $itemCount)) {
    header ('Retry-After: ' . $limiter->retryAfter (3600));
    // 429
}
$limiter->cleanup ();  // from a daily cron: drops windows older than a day

The application owns the table. Default name neuron_rate_limits (pass another name to DatabaseStore; it must match /^[A-Za-z0-9_]+$/ and is quoted with backticks in every statement):

CREATE TABLE neuron_rate_limits (
  id int unsigned NOT NULL AUTO_INCREMENT,
  rl_key varchar(128) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL,
  window_start int unsigned NOT NULL,
  hits int unsigned NOT NULL DEFAULT 0,
  PRIMARY KEY (id),
  UNIQUE KEY neuron_rate_limits_key_window (rl_key, window_start),
  KEY neuron_rate_limits_window (window_start)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

rl_key uses a binary (case-sensitive) collation so keys match exactly; a case-insensitive collation would merge keys that differ only by case into the same bucket. neuron_rate_limits_window keeps the cleanup DELETE (which scans by window_start) indexed. A table with PRIMARY KEY (rl_key, window_start) and no id works too.

A few contract details worth knowing:

• Key length. rl_key is varchar(128). INSERT IGNORE silently truncates a longer key to fit instead of erroring, so two distinct keys that only differ past the 128th character would share a bucket. Keep keys short, or hash the long/variable part before using it as a key.
• max < 1 refuses every attempt. There's no special-casing: a cap below 1 can never be satisfied. If 0 should mean "disabled" (skip rate limiting entirely) in your application, guard for that case before calling attempt().
• remaining() is a non-atomic read. It issues a plain SELECT with no lock, so its result can be stale relative to a concurrent attempt() against the same key and window.
• Don't call attempt() inside a long-running explicit transaction. A rollback refunds the budget the INSERT/UPDATE charged, and holding that row's locks open for the rest of a long transaction can deadlock against other writers hitting the same key.
• window_start is an unsigned 32-bit epoch bucket (seconds since the epoch, rounded down to a window boundary), matching the column's int unsigned type above.