Rate Limiting & Quotas

SkySend includes built-in rate limiting and upload quotas to protect against abuse.

Rate Limiting

Rate limiting applies to all API endpoints. It uses a sliding window algorithm per IP address.

Variable	Default	Description
RATE_LIMIT_WINDOW	60000	Window size in milliseconds (default: 1 minute)
RATE_LIMIT_MAX	60	Maximum requests per window per IP

Response Headers

Every response includes rate limit headers:

X-RateLimit-Limit: 60
X-RateLimit-Remaining: 57
X-RateLimit-Reset: 1704067260000

When the limit is exceeded, the server returns 429 Too Many Requests.

Configuration Examples

# Strict: 20 requests per minute
RATE_LIMIT_WINDOW=60000
RATE_LIMIT_MAX=20

# Relaxed: 200 requests per 5 minutes
RATE_LIMIT_WINDOW=300000
RATE_LIMIT_MAX=200

Upload Quotas

Upload quotas limit the total volume of data a single user can upload within a time window. This prevents a single user from filling up the server's storage.

Variable	Default	Description
UPLOAD_QUOTA_BYTES	0	Maximum bytes per user per window. 0 = disabled
UPLOAD_QUOTA_WINDOW	86400	Window size in seconds (default: 24 hours)

Configuration Examples

# 10 GB per user per day
UPLOAD_QUOTA_BYTES=10737418240
UPLOAD_QUOTA_WINDOW=86400

# 1 GB per user per hour
UPLOAD_QUOTA_BYTES=1073741824
UPLOAD_QUOTA_WINDOW=3600

Privacy

Upload quotas use HMAC-SHA256 to hash IP addresses before storing them. The HMAC key rotates daily, which means:

• No plaintext IP addresses are ever stored
• IP hashes cannot be correlated across days
• When the key rotates, the entire quota store is cleared

This design ensures that SkySend enforces quotas without compromising user privacy.

Behavior

When a quota is exceeded, the server returns 429 Too Many Requests with a message indicating when the quota resets:

{
  "error": "Upload quota exceeded",
  "retryAfter": 3600
}

IP Detection

SkySend determines the client IP using:

1. X-Forwarded-For header (if TRUST_PROXY=true)
2. X-Real-IP header (if TRUST_PROXY=true)
3. Direct socket address (fallback)

WARNING

Only enable TRUST_PROXY=true when running behind a trusted reverse proxy. Otherwise, clients can spoof their IP to bypass rate limits and quotas.