/**
 * Manages certificate provisioning scheduling with:
 * - Per-domain exponential backoff persisted via CertBackoffDoc
 *
 * Note: Serial stagger queue was removed — smartacme v9 handles
 * concurrency, per-domain dedup, and rate limiting internally.
 */
export declare class CertProvisionScheduler {
    private maxBackoffHours;
    private backoffCache;
    constructor(options?: {
        maxBackoffHours?: number;
    });
    /**
     * Sanitized domain key for storage lookups
     */
    private sanitizeDomain;
    /**
     * Load backoff entry from database (with in-memory cache)
     */
    private loadBackoff;
    /**
     * Save backoff entry to both cache and database
     */
    private saveBackoff;
    /**
     * Check if a domain is currently in backoff.
     * Expired entries are pruned from the cache to prevent unbounded growth.
     */
    isInBackoff(domain: string): Promise<boolean>;
    /**
     * Record a provisioning failure for a domain.
     * Sets exponential backoff: min(failures^2 * 1h, maxBackoffHours)
     */
    recordFailure(domain: string, error?: string): Promise<void>;
    /**
     * Clear backoff for a domain (on success or manual override)
     */
    clearBackoff(domain: string): Promise<void>;
    /**
     * Clear all in-memory backoff cache entries
     */
    clear(): void;
    /**
     * Get backoff info for UI display
     */
    getBackoffInfo(domain: string): Promise<{
        failures: number;
        retryAfter?: string;
        lastError?: string;
    } | null>;
}