API Gateway Request Throttling: Protect Backends (Kong, APISIX, AWS)

Imagine running a promotion and your backend collapsing under a flood of requests. At peak load of 10,000 rps, in-app rate limiting fails to sync between services — each microservice holds its own counter, and a burst causes limit overruns of 200%. Centralized request throttling via an API Gateway is the single control point where policies are applied to all traffic without changing business logic. We audited a fintech client: after implementing Kong rate limiting, 429 errors dropped by 90%, and backend load by 70%.

Why API Gateway Instead of In-App Rate Limiting?

An in-app solution requires changes in every service, code duplication, and coordination. A Gateway is a single layer where policies are applied uniformly. No need to touch business logic — just configure a plugin. Plus, unified monitoring, logging, and the ability to change limits on the fly without deployments.

Comparison of approaches:

Which Algorithm to Choose?

There are several algorithms, and the choice depends on the load profile. Token Bucket (used by Kong) allows bursts up to a configurable limit, whereas Leaky Bucket (available in APISIX) smoothens traffic. Fixed Window is simple but has edge effects; Sliding Window offers high accuracy.

Configuration on Specific Gateways

Configuration in Kong

Kong supports multi-level limits: global, per service, per consumer. Uses Redis for synchronization. Example via Admin API:

# Global limit (all services) — 1000 requests per minute
curl -X POST http://localhost:8001/plugins \
  -d "name=rate-limiting" \
  -d "config.minute=1000" \
  -d "config.hour=20000" \
  -d "config.policy=redis" \
  -d "config.redis_host=redis" \
  -d "config.limit_by=ip"

# Limit at service level for payments-api — 10 rps
curl -X POST http://localhost:8001/services/payments-api/plugins \
  -d "name=rate-limiting" \
  -d "config.second=10" \
  -d "config.minute=200" \
  -d "config.limit_by=consumer"

# Limit for consumer free-tier — 60 requests per minute
curl -X POST http://localhost:8001/consumers/free-tier/plugins \
  -d "name=rate-limiting" \
  -d "config.minute=60" \
  -d "config.hour=500"

Response headers contain limit and reset time. Official documentation: Kong Rate Limiting.

Configuration in APISIX

APISIX provides three plugins: limit-count (counter), limit-req (leaky bucket), limit-conn (concurrent connections). Example via Admin API:

{
  "plugins": {
    "limit-count": {
      "count": 100,
      "time_window": 60,
      "rejected_code": 429,
      "rejected_msg": "Too many requests",
      "key": "consumer_name",
      "policy": "redis",
      "redis_host": "redis",
      "redis_port": 6379,
      "redis_database": 0,
      "show_limit_quota_header": true
    },
    "limit-req": {
      "rate": 10,
      "burst": 5,
      "key": "remote_addr",
      "rejected_code": 429
    },
    "limit-conn": {
      "conn": 50,
      "burst": 10,
      "key": "remote_addr",
      "rejected_code": 503
    }
  }
}

limit-req implements Leaky Bucket — requests beyond the rate go into a burst queue, then 429. limit-conn limits concurrent connections. APISIX's limit-req plugin provides 2x better burst control than fixed window approaches.

Configuration in AWS API Gateway

AWS uses Usage Plans with throttle and quota. Example Terraform for four tiers:

resource "aws_api_gateway_usage_plan" "tiers" {
  for_each = {
    free    = { rate = 10,  burst = 5,   quota = 1000,   period = "DAY" }
    basic   = { rate = 50,  burst = 25,  quota = 10000,  period = "DAY" }
    pro     = { rate = 200, burst = 100, quota = 100000, period = "DAY" }
    enterprise = { rate = 1000, burst = 500, quota = 0, period = "DAY" }
  }

  name = "plan-${each.key}"

  api_stages {
    api_id = aws_api_gateway_rest_api.main.id
    stage  = "prod"
  }

  throttle_settings {
    rate_limit  = each.value.rate
    burst_limit = each.value.burst
  }

  dynamic "quota_settings" {
    for_each = each.value.quota > 0 ? [1] : []
    content {
      limit  = each.value.quota
      period = each.value.period
    }
  }
}

Dynamic Throttling by Business Attributes

Rate limits don't always depend solely on IP or API key. Often logic is needed: user subscription, resource type, time of day. Example custom Kong plugin that fetches limits from a billing service:

local function get_rate_limit(consumer_id)
  local cache_key = "rate:" .. consumer_id
  local cached = kong.cache:get(cache_key)
  if cached then return cached end

  -- Request to billing service
  local client = httpc.new()
  local res = client:request_uri("http://billing-service/limits/" .. consumer_id)
  local limits = cjson.decode(res.body)

  kong.cache:set(cache_key, limits, 300)  -- cache 5 minutes
  return limits
end

local limits = get_rate_limit(consumer_id)
-- limits = { minute: 1000, hour: 10000 }

Common Mistakes and How to Avoid Them

• Burst not configured: even legitimate spikes are rejected. Set burst to 50-100% of rate.
• No whitelist for internal services: monitoring fails. Use ip-restriction plugin with network ranges.
• Using Fixed Window without considering window edge: load at window boundaries doubles. Use Sliding Window or Leaky Bucket.
• Not setting Retry-After header: clients don't know when to retry. Always include Retry-After in 429 responses.
• Redis without replication: if Redis goes down, limits reset. Use Redis cluster or configure a replica.

Implementation and Pricing

1. Audit of current API architecture and selection of optimal Gateway.
2. Designing policies: global, per service, per user.
3. Setting up Redis for synchronization (if needed).
4. Integration with monitoring (Prometheus, Grafana) for limit visualization.
5. Documentation of the rate limiting scheme for the development team.
6. Engineer training (2-3 hour workshop).
7. SLA guarantee of 99.9% during operation.

Basic multi-level throttling (by IP, consumer, service) with Redis takes 2 to 5 working days depending on integration complexity. Basic setup starts at $500, including Redis sync and default policies. Dynamic user-specific limits and custom monitoring range from $2,000 to $5,000. We calculate exact cost after auditing your architecture. With 5+ years of experience and over 50 API Gateway projects completed, we guarantee a reliable solution.

Contact us for a free consultation — we'll select the optimal request throttling strategy for your load. Get backend protection starting from $500.

Note: Sliding Window algorithm provides highest accuracy for critical APIs.

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.