Implementing Rate Limiting for Web APIs

Imagine your API crashing under load, with thousands of requests from a single IP in the logs. On one of our projects, a third‑party service got stuck in a loop, sending 10,000 requests per minute. Without rate limiting, it took down the database and caused 4 hours of downtime. We deployed limits at both Nginx and application levels—the problem never returned. Such cases are our daily bread.

We implement rate limiting for web application APIs on any stack—from Laravel to NestJS—with Redis backend, tier‑based limits, and proper response headers. Below are battle‑tested approaches to help you avoid downtime and protect your infrastructure.

How to Choose a Rate Limiting Algorithm

The choice depends on the traffic pattern. Sliding Window averages requests over a moving window, avoiding the Fixed Window vulnerability: when the counter resets every N seconds, a client can send 100 requests at the end of the window and 100 at the start of the next—effectively 200 per second. Sliding Window prevents this. Token Bucket accumulates tokens at a refill rate, allowing bursts up to the bucket size—ideal for integrations with irregular traffic. Leaky Bucket queues requests with a fixed drain rate, providing the smoothest load but potentially causing delays.

For most web applications, Sliding Window with Redis is optimal. It provides even throttling without spikes at window edges. If your API handles burst traffic (e.g., from partner integrations), choose Token Bucket. For real‑time systems with a steady stream, Leaky Bucket is best.

Why Combine Nginx and Application Rate Limiting?

Nginx acts as the first line of defense: it can block obvious anomalies (e.g., more than 1000 requests per second from a single IP) at the server level, without burdening the application. The application then provides flexible per‑user and per‑tier limits. This two‑layer protection is more effective than any single‑layer implementation. You can configure Nginx with the limit_req module for general protection, and set finer rules in the application.

Implementation in Laravel and NestJS

Laravel — using Throttle middleware and RateLimiter:

// app/Providers/RouteServiceProvider.php
RateLimiter::for('api', function (Request $request) {
    $user = $request->user();
    if (!$user) return Limit::perMinute(30)->by($request->ip());
    return match($user->plan) {
        'enterprise' => Limit::perMinute(1000)->by($user->id),
        'pro'        => Limit::perMinute(300)->by($user->id),
        default      => Limit::perMinute(60)->by($user->id),
    };
});

Route::middleware(['auth:sanctum', 'throttle:api'])->group(function () {
    Route::apiResource('articles', ArticleController::class);
});

NestJS — using the @nestjs/throttler module with Redis storage:

import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';
import { ThrottlerStorageRedisService } from 'nestjs-throttler-storage-redis';

ThrottlerModule.forRoot({
  throttlers: [
    { name: 'short', ttl: 1000, limit: 10 },
    { name: 'medium', ttl: 60000, limit: 300 },
    { name: 'long', ttl: 3600000, limit: 5000 },
  ],
  storage: new ThrottlerStorageRedisService(redisClient),
});

Distributed Rate Limiting with a Lua Script

For multi‑server applications, we use a centralized Redis and an atomic Lua counter:

-- sliding_window.lua
local key = KEYS[1]
local now = tonumber(ARGV[1])
local window = tonumber(ARGV[2])
local limit = tonumber(ARGV[3])

redis.call('ZREMRANGEBYSCORE', key, 0, now - window)
local count = redis.call('ZCARD', key)

if count < limit then
    redis.call('ZADD', key, now, now .. math.random())
    redis.call('EXPIRE', key, window / 1000)
    return 1
end
return 0

This script guarantees atomicity and works in distributed architectures. We use it in high‑load projects.

Bypass Strategies: What Not to Limit

Some requests must bypass limits: internal services (IP whitelist), webhook endpoints, health checks /health. Implement via a condition in the RateLimiter:

RateLimiter::for('api', function (Request $request) {
    if ($request->ip() === config('services.internal_ip')) {
        return Limit::none();
    }
    // ...
});

Common Mistakes When Implementing Rate Limiting

In 70% of projects we've audited, Fixed Window is used without considering bursts—allowing clients to bypass the limit. Another 20% ignore Retry-After headers, leaving clients unaware of when to retry. Limiting health checks causes false monitoring alerts. Ignoring distributed storage leads to inconsistent counters across servers.

What’s Included in a Turnkey Implementation

1. Analysis of current architecture and traffic profile.
2. Algorithm selection (we recommend Sliding Window + Redis).
3. Configuration of limits per endpoint and tier.
4. Integration with Nginx as the first line of defense.
5. Addition of X-RateLimit-* and Retry-After headers.
6. Monitoring of 429 responses (Grafana + alerts).
7. Documentation and team training.

Timeline

Basic implementation with Redis and Sliding Window: 1–2 days. Extended with Nginx, Lua scripts, and monitoring: 3–4 days. The cost is calculated individually after analyzing your project. We evaluate your project in 1 day—contact us for a consultation. Order rate limiting implementation, and your API will withstand any load.

We have implemented rate limiting for 20+ projects of varying complexity. Rest assured, after our deployment, you will forget about overload issues.

Web Application Security: HTTPS, CSP, XSS, CSRF, WAF, DDoS Protection

A website breach rarely looks like in movies. More often it's: a bot finds an unprotected /admin/export endpoint, downloads the customer database, and closes the connection. Or: through an outdated WordPress plugin, a web shell is uploaded, and the server starts sending spam. Or quieter: an XSS in a comment field allows stealing admin session cookies, unnoticed for months. We have analyzed dozens of such cases — each vulnerability could have been fixed at the development or audit stage.

Web application security is not a single setting. It's layers of protection, each closing a separate class of attacks. Order an audit — we'll assess the project and deliver a turnkey plan within 2–4 weeks.

How do we ensure comprehensive web application security?

HTTPS and Proper TLS Configuration

HTTPS is the minimum mandatory level. But having an SSL certificate and having a properly configured TLS are different things.

In Nginx/Apache configuration we check:

• Protocols: only TLS 1.2 and TLS 1.3, SSLv3 and TLS 1.0/1.1 are disabled
• Cipher suites: prefer ECDHE (Forward Secrecy), remove NULL, RC4, DES, 3DES
• HSTS (Strict-Transport-Security: max-age=31536000; includeSubDomains; preload) — browser will never make insecure requests
• OCSP Stapling — speeds up certificate revocation check
• Redirect 301 from HTTP to HTTPS — both in server config and code (double redirect causes SEO weight loss)

Check: SSL Labs (ssllabs.com/ssltest) should show A or A+. If B, the configuration is weak.

Let's Encrypt + Certbot for production is standard. Automatic renewal via certbot renew in cron. Wildcard certificates for subdomains via DNS-01 challenge.

Content Security Policy: The Most Powerful and Complex Protection

CSP is an HTTP header that tells the browser which sources are allowed to load resources. A properly configured CSP completely blocks most XSS attacks, even if the vulnerability exists in the code.

The problem: breaking the site with an incorrect CSP is easy. default-src 'none' — and fonts, images, JS stop working. So we start with Content-Security-Policy-Report-Only — CSP logs violations but does not block anything. We monitor reports for 2–4 weeks, refine the policy, then switch to enforcement mode.

Example of a real policy for a site with Google Analytics, Google Fonts, and Stripe:

Content-Security-Policy:
  default-src 'self';
  script-src 'self' https://www.googletagmanager.com https://js.stripe.com 'nonce-{random}';
  style-src 'self' https://fonts.googleapis.com 'unsafe-inline';
  font-src 'self' https://fonts.gstatic.com;
  frame-src https://js.stripe.com;
  img-src 'self' data: https://www.google-analytics.com;
  connect-src 'self' https://api.stripe.com https://www.google-analytics.com;
  report-uri /csp-report;

nonce — a random string generated server-side per request. Inline scripts with the correct nonce are allowed; without nonce, they are blocked. This completely breaks XSS via <script>alert(1)</script>.

'unsafe-inline' in style-src is a compromise for inline styles. It's better to remove it by moving all styles to CSS files, but that requires refactoring.

Why XSS Remains the Most Common Vulnerability?

XSS (Cross-Site Scripting) — injection of JS code through user input. According to OWASP, XSS is in the top 3 web application vulnerabilities. Three types:

Protection: never insert user input into HTML without escaping. In PHP — htmlspecialchars() with ENT_QUOTES. In Laravel Blade templates — {{ $var }} is safe, {!! $var !!} is dangerous. In React — {variable} is safe, dangerouslySetInnerHTML is dangerous. For Rich Text — use htmlpurifier on PHP or DOMPurify in the browser.

CSRF: Protecting Forms and APIs

CSRF (Cross-Site Request Forgery) — an attacker forces the victim's browser to send a request on their behalf. Example: a user is logged into a bank, opens a malicious page, which makes fetch('https://bank.ru/transfer?to=evil&amount=50000') — if the bank is unprotected, money is transferred.

CSRF tokens — standard protection for forms: the server generates a random token, stores it in the session, and inserts it as a hidden field in the form. On POST request, the token is verified. The attacker does not know the token. Laravel does this automatically with @csrf.

SameSite cookies — modern protection: SameSite=Strict or SameSite=Lax prevents the browser from sending cookies in cross-site requests. Works in all modern browsers.

API without sessions (JWT, Bearer tokens) — CSRF is irrelevant if the token is not stored in a cookie (but in the Authorization header or localStorage). However, localStorage is vulnerable to XSS — so for sensitive data, HttpOnly cookies with SameSite are preferable.

WAF and DDoS Protection

WAF (Web Application Firewall) filters HTTP traffic for attacks: SQL injection, XSS, path traversal, known exploit patterns. Options:

• Cloudflare WAF — cloud-based, OWASP Top 10 rules out of the box, custom rules via expressions. Managed Rules automatically block new threats.
• ModSecurity (Nginx/Apache) — self-hosted, OWASP Core Rule Set (CRS). Flexible but requires tuning and monitoring of false positives.
• AWS WAF — for infrastructure on AWS, integrates with CloudFront and ALB.

DDoS protection. Cloudflare at L3/L4/L7 is the de facto standard for most sites. Automatic mitigation of volumetric attacks, Under Attack Mode during active attacks. For critical infrastructure — Cloudflare Magic Transit or specialized solutions (Qrator, StormWall for the Russian market).

Rate Limiting at the application level — an additional layer. Laravel ThrottleRequests middleware: 60 requests per minute per IP for general endpoints, 5 for /login and /password/reset. Redis as a counter store — mandatory for horizontally scalable systems (otherwise limits are not synchronized between servers).

Other Mandatory Measures

Security headers. Besides CSP: X-Frame-Options: DENY (clickjacking protection), X-Content-Type-Options: nosniff (MIME sniffing), Referrer-Policy: strict-origin-when-cross-origin, Permissions-Policy (restrict browser API access: camera, microphone, geolocation).

SQL injection. Prepared statements everywhere. No concatenation of user input into SQL strings. ORM (Eloquent, Doctrine) protects by default. $wpdb->prepare() in WordPress is mandatory.

Dependency updates. composer audit and npm audit in CI/CD pipeline. Dependabot or Renovate for automatic PRs with updates. Critical CVEs — patch within 24 hours.

Secrets and configuration. .env — never in Git. Secrets in production — via CI/CD environment variables (GitHub Secrets, GitLab CI Variables) or HashiCorp Vault. Leak detection: git-secrets, truffleHog in pre-commit hooks.

How We Work

1. Audit — code scanning, configuration review, dependency analysis, manual business logic verification.
2. Planning — vulnerability remediation plan, stack selection (CSP, WAF, rate limiting).
3. Implementation — TLS setup, CSP configuration, headers, Rate Limiting, WAF.
4. Testing — re-penetration test, load testing, false positive check.
5. Deployment and Monitoring — enable production CSP, set up alerts, train the team.

What's Included

• Report with found vulnerabilities and recommendations (PDF + code snippets)
• Ready TLS configuration (Nginx/Apache)
• CSP policy with Report-Only and production versions
• WAF and Rate Limiting setup
• Dependency update plan
• Access to monitoring tools (Sentry, Datadog)
• 30 days of post-audit support (consultations, fixes)

Timeline and Cost

The budget is calculated individually — contact us for a project evaluation.