diff --git a/src/constants/index.ts b/src/constants/index.ts
new file mode 100644
index 0000000..fd5954e
--- /dev/null
+++ b/src/constants/index.ts
@@ -0,0 +1,180 @@
+/**
+ * Constants for telegram-bot-workers
+ *
+ * Centralized magic strings and configuration values for better maintainability.
+ *
+ * Usage:
+ *   import { SESSION_KEYS, MESSAGE_MARKERS, sessionKey } from './constants';
+ *   const key = sessionKey(SESSION_KEYS.DELETE_CONFIRM, userId);
+ */
+
+/**
+ * Session key prefixes for KV storage
+ */
+export const SESSION_KEYS = {
+  DELETE_CONFIRM: 'delete_confirm',
+  SERVER_ORDER_CONFIRM: 'server_order_confirm',
+  SERVER_SESSION: 'server_session',
+  RATE_LIMIT: 'rate_limit',
+  NOTIFICATION: 'notification',
+} as const;
+
+/**
+ * Message markers for AI response processing
+ *
+ * These markers control how responses are processed:
+ * - DIRECT: Pass through response without AI reinterpretation
+ * - KEYBOARD: Indicates inline keyboard JSON data follows
+ * - KEYBOARD_END: Marks end of keyboard data
+ * - PASSTHROUGH: Return to normal conversation flow
+ */
+export const MESSAGE_MARKERS = {
+  DIRECT: '__DIRECT__',
+  KEYBOARD: '__KEYBOARD__',
+  KEYBOARD_END: '__END__',
+  PASSTHROUGH: '__PASSTHROUGH__',
+} as const;
+
+/**
+ * Keyboard types for inline buttons
+ */
+export const KEYBOARD_TYPES = {
+  DOMAIN_REGISTER: 'domain_register',
+  SERVER_ORDER: 'server_order',
+} as const;
+
+/**
+ * Callback data prefixes for inline keyboard buttons
+ *
+ * Format: prefix:action:params
+ * Examples:
+ *   - domain_reg:confirm:example.com:15000
+ *   - server_order:confirm:order_123
+ */
+export const CALLBACK_PREFIXES = {
+  DOMAIN_REGISTER_CONFIRM: 'confirm_domain_register',
+  DOMAIN_REGISTER_CANCEL: 'cancel_domain_register',
+  SERVER_ORDER_CONFIRM: 'confirm_server_order',
+  SERVER_ORDER_CANCEL: 'cancel_server_order',
+  DELETE_CONFIRM: 'confirm_delete',
+  DELETE_CANCEL: 'cancel_delete',
+} as const;
+
+/**
+ * Transaction statuses for deposit system
+ */
+export const TRANSACTION_STATUS = {
+  PENDING: 'pending',
+  CONFIRMED: 'confirmed',
+  CANCELLED: 'cancelled',
+  REJECTED: 'rejected',
+} as const;
+
+/**
+ * Transaction types for deposit system
+ */
+export const TRANSACTION_TYPE = {
+  DEPOSIT: 'deposit',
+  WITHDRAWAL: 'withdrawal',
+  REFUND: 'refund',
+} as const;
+
+/**
+ * Server order statuses
+ */
+export const SERVER_ORDER_STATUS = {
+  PENDING: 'pending',
+  PROVISIONING: 'provisioning',
+  ACTIVE: 'active',
+  SUSPENDED: 'suspended',
+  TERMINATED: 'terminated',
+  FAILED: 'failed',
+} as const;
+
+/**
+ * Server actions
+ */
+export const SERVER_ACTION = {
+  RECOMMEND: 'recommend',
+  ORDER: 'order',
+  START: 'start',
+  STOP: 'stop',
+  DELETE: 'delete',
+  LIST: 'list',
+  INFO: 'info',
+  IMAGES: 'images',
+} as const;
+
+/**
+ * Domain actions
+ */
+export const DOMAIN_ACTION = {
+  REGISTER: 'register',
+  CHECK: 'check',
+  WHOIS: 'whois',
+  LIST: 'list',
+  INFO: 'info',
+  GET_NS: 'get_ns',
+  SET_NS: 'set_ns',
+  PRICE: 'price',
+  CHEAPEST: 'cheapest',
+} as const;
+
+/**
+ * Deposit actions
+ */
+export const DEPOSIT_ACTION = {
+  BALANCE: 'balance',
+  ACCOUNT: 'account',
+  REQUEST: 'request',
+  HISTORY: 'history',
+  CANCEL: 'cancel',
+  PENDING: 'pending',
+  CONFIRM: 'confirm',
+  REJECT: 'reject',
+} as const;
+
+/**
+ * Helper to create session key with user ID
+ *
+ * @param prefix - Session key prefix (from SESSION_KEYS)
+ * @param userId - User ID (telegram_id or user identifier)
+ * @returns Formatted session key
+ *
+ * @example
+ * const key = sessionKey(SESSION_KEYS.DELETE_CONFIRM, '123456');
+ * // Returns: 'delete_confirm:123456'
+ */
+export function sessionKey(prefix: string, userId: string | number): string {
+  return `${prefix}:${userId}`;
+}
+
+/**
+ * Helper to parse session key
+ *
+ * @param key - Full session key
+ * @returns Object with prefix and userId, or null if invalid
+ *
+ * @example
+ * const parsed = parseSessionKey('delete_confirm:123456');
+ * // Returns: { prefix: 'delete_confirm', userId: '123456' }
+ */
+export function parseSessionKey(key: string): { prefix: string; userId: string } | null {
+  const parts = key.split(':');
+  if (parts.length !== 2) return null;
+  return { prefix: parts[0], userId: parts[1] };
+}
+
+/**
+ * Type guards for type safety
+ */
+export type SessionKeyPrefix = typeof SESSION_KEYS[keyof typeof SESSION_KEYS];
+export type MessageMarker = typeof MESSAGE_MARKERS[keyof typeof MESSAGE_MARKERS];
+export type KeyboardType = typeof KEYBOARD_TYPES[keyof typeof KEYBOARD_TYPES];
+export type CallbackPrefix = typeof CALLBACK_PREFIXES[keyof typeof CALLBACK_PREFIXES];
+export type TransactionStatus = typeof TRANSACTION_STATUS[keyof typeof TRANSACTION_STATUS];
+export type TransactionType = typeof TRANSACTION_TYPE[keyof typeof TRANSACTION_TYPE];
+export type ServerOrderStatus = typeof SERVER_ORDER_STATUS[keyof typeof SERVER_ORDER_STATUS];
+export type ServerAction = typeof SERVER_ACTION[keyof typeof SERVER_ACTION];
+export type DomainAction = typeof DOMAIN_ACTION[keyof typeof DOMAIN_ACTION];
+export type DepositAction = typeof DEPOSIT_ACTION[keyof typeof DEPOSIT_ACTION];
diff --git a/src/security.ts b/src/security.ts
index 606f4b2..3fecae1 100644
--- a/src/security.ts
+++ b/src/security.ts
@@ -138,6 +138,8 @@ export async function validateWebhookRequest(
 }
 
 // Rate Limiting (Cloudflare KV 기반)
+// NOTE: Future migration to KVCache abstraction layer (kv-cache.ts) planned
+// Current implementation kept for backward compatibility
 interface RateLimitData {
   count: number;
   resetAt: number;
diff --git a/src/server-provision.ts b/src/server-provision.ts
index 64b5120..6699b44 100644
--- a/src/server-provision.ts
+++ b/src/server-provision.ts
@@ -238,7 +238,7 @@ async function callCloudOrchestrator(
 
   const data = await response.json() as ProvisionResponse;
 
-  logger.info('Cloud Orchestrator API 응답', data);
+  logger.info('Cloud Orchestrator API 응답', { response: data });
 
   if (!data.success) {
     throw new Error(data.error || 'Provisioning failed');
diff --git a/src/services/kv-cache.ts b/src/services/kv-cache.ts
new file mode 100644
index 0000000..00a1af9
--- /dev/null
+++ b/src/services/kv-cache.ts
@@ -0,0 +1,124 @@
+import { createLogger } from '../utils/logger';
+
+const logger = createLogger('kv-cache');
+
+/**
+ * KV Cache abstraction layer for consistent caching patterns
+ */
+export class KVCache {
+  constructor(private kv: KVNamespace, private prefix: string = '') {}
+
+  /**
+   * Get value from cache
+   */
+  async get<T>(key: string): Promise<T | null> {
+    const fullKey = this.prefix ? `${this.prefix}:${key}` : key;
+    try {
+      const value = await this.kv.get(fullKey, 'json');
+      return value as T | null;
+    } catch (error) {
+      logger.error('KV get failed', error as Error, { key: fullKey });
+      return null;
+    }
+  }
+
+  /**
+   * Set value in cache with optional TTL
+   */
+  async set<T>(key: string, value: T, ttlSeconds?: number): Promise<boolean> {
+    const fullKey = this.prefix ? `${this.prefix}:${key}` : key;
+    try {
+      const options = ttlSeconds ? { expirationTtl: ttlSeconds } : undefined;
+      await this.kv.put(fullKey, JSON.stringify(value), options);
+      return true;
+    } catch (error) {
+      logger.error('KV set failed', error as Error, { key: fullKey });
+      return false;
+    }
+  }
+
+  /**
+   * Delete value from cache
+   */
+  async delete(key: string): Promise<boolean> {
+    const fullKey = this.prefix ? `${this.prefix}:${key}` : key;
+    try {
+      await this.kv.delete(fullKey);
+      return true;
+    } catch (error) {
+      logger.error('KV delete failed', error as Error, { key: fullKey });
+      return false;
+    }
+  }
+
+  /**
+   * Get or set pattern - fetch from cache or compute and store
+   */
+  async getOrSet<T>(
+    key: string,
+    factory: () => Promise<T>,
+    ttlSeconds?: number
+  ): Promise<T> {
+    const cached = await this.get<T>(key);
+    if (cached !== null) {
+      logger.debug('Cache hit', { key });
+      return cached;
+    }
+
+    logger.debug('Cache miss', { key });
+    const value = await factory();
+    await this.set(key, value, ttlSeconds);
+    return value;
+  }
+
+  /**
+   * Check if key exists
+   */
+  async exists(key: string): Promise<boolean> {
+    const value = await this.get(key);
+    return value !== null;
+  }
+}
+
+/**
+ * Create rate limiter cache instance
+ */
+export function createRateLimitCache(kv: KVNamespace): KVCache {
+  return new KVCache(kv, 'rate');
+}
+
+/**
+ * Create session cache instance
+ */
+export function createSessionCache(kv: KVNamespace): KVCache {
+  return new KVCache(kv, 'session');
+}
+
+/**
+ * Rate limiting helper - returns true if request should be allowed
+ */
+export async function checkRateLimitWithCache(
+  cache: KVCache,
+  userId: string,
+  maxRequests: number = 30,
+  windowSeconds: number = 60
+): Promise<boolean> {
+  const key = userId;
+  const now = Math.floor(Date.now() / 1000);
+
+  const data = await cache.get<{ count: number; windowStart: number }>(key);
+
+  if (!data || now - data.windowStart >= windowSeconds) {
+    // New window
+    await cache.set(key, { count: 1, windowStart: now }, windowSeconds);
+    return true;
+  }
+
+  if (data.count >= maxRequests) {
+    return false; // Rate limited
+  }
+
+  // Increment count
+  await cache.set(key, { count: data.count + 1, windowStart: data.windowStart }, windowSeconds);
+  return true;
+}
diff --git a/src/utils/env-validation.ts b/src/utils/env-validation.ts
new file mode 100644
index 0000000..e6ae83f
--- /dev/null
+++ b/src/utils/env-validation.ts
@@ -0,0 +1,105 @@
+import { z } from 'zod';
+import { createLogger } from './logger';
+
+const logger = createLogger('env-validation');
+
+/**
+ * Environment variable schema with validation rules
+ */
+export const EnvSchema = z.object({
+  // Required secrets
+  BOT_TOKEN: z.string().min(1, 'BOT_TOKEN is required'),
+  WEBHOOK_SECRET: z.string().min(10, 'WEBHOOK_SECRET must be at least 10 characters'),
+
+  // Optional secrets with defaults handled elsewhere
+  OPENAI_API_KEY: z.string().optional(),
+  DEPOSIT_API_SECRET: z.string().optional(),
+  BRAVE_API_KEY: z.string().optional(),
+  NAMECHEAP_API_KEY: z.string().optional(),
+  NAMECHEAP_API_KEY_INTERNAL: z.string().optional(),
+
+  // Configuration with defaults
+  ENVIRONMENT: z.enum(['development', 'production']).default('production'),
+  SUMMARY_THRESHOLD: z.string().default('20').transform(Number),
+  MAX_SUMMARIES_PER_USER: z.string().default('3').transform(Number),
+
+  // Admin IDs
+  DOMAIN_OWNER_ID: z.string().optional(),
+  DEPOSIT_ADMIN_ID: z.string().optional(),
+
+  // API URLs (optional, have defaults in code)
+  OPENAI_API_BASE: z.string().url().optional(),
+  NAMECHEAP_API_URL: z.string().url().optional(),
+  WHOIS_API_URL: z.string().url().optional(),
+  CONTEXT7_API_BASE: z.string().url().optional(),
+  BRAVE_API_BASE: z.string().url().optional(),
+  WTTR_IN_URL: z.string().url().optional(),
+  HOSTING_SITE_URL: z.string().url().optional(),
+  CLOUD_ORCHESTRATOR_URL: z.string().url().optional(),
+});
+
+export type ValidatedEnv = z.infer<typeof EnvSchema>;
+
+/**
+ * Validation result type
+ */
+export interface EnvValidationResult {
+  success: boolean;
+  errors: string[];
+  warnings: string[];
+}
+
+/**
+ * Validate environment variables
+ * Call this early in worker initialization
+ */
+export function validateEnv(env: Record<string, unknown>): EnvValidationResult {
+  const result: EnvValidationResult = {
+    success: true,
+    errors: [],
+    warnings: [],
+  };
+
+  // Validate with Zod
+  const parsed = EnvSchema.safeParse(env);
+
+  if (!parsed.success) {
+    result.success = false;
+    for (const issue of parsed.error.issues) {
+      const path = issue.path.join('.');
+      result.errors.push(`${path}: ${issue.message}`);
+    }
+  }
+
+  // Additional warnings for recommended but optional vars
+  if (!env.OPENAI_API_KEY) {
+    result.warnings.push('OPENAI_API_KEY not set - will use Workers AI fallback');
+  }
+
+  if (!env.DEPOSIT_ADMIN_ID) {
+    result.warnings.push('DEPOSIT_ADMIN_ID not set - admin notifications disabled');
+  }
+
+  // Log results
+  if (result.errors.length > 0) {
+    logger.error('Environment validation failed', new Error('Invalid configuration'), {
+      errors: result.errors,
+    });
+  }
+
+  if (result.warnings.length > 0) {
+    logger.warn('Environment validation warnings', { warnings: result.warnings });
+  }
+
+  return result;
+}
+
+/**
+ * Quick check for critical env vars - throws on failure
+ */
+export function requireEnv(env: Record<string, unknown>, keys: string[]): void {
+  const missing = keys.filter(key => !env[key]);
+  if (missing.length > 0) {
+    throw new Error(`Missing required environment variables: ${missing.join(', ')}`);
+  }
+}
diff --git a/src/utils/logger.ts b/src/utils/logger.ts
index 1999ef3..f99e8e8 100644
--- a/src/utils/logger.ts
+++ b/src/utils/logger.ts
@@ -35,6 +35,31 @@ export enum LogLevel {
   FATAL = 'FATAL',
 }
 
+/**
+ * 로그 컨텍스트 값 타입
+ *
+ * any 대신 unknown을 사용하여 타입 안정성 개선
+ * - unknown은 사용 전 타입 체크를 강제하므로 any보다 안전
+ * - 모든 타입의 값을 저장 가능하지만, 사용 시 타입 검증 필요
+ *
+ * 기본 타입 (string, number, boolean 등)과 객체/배열 모두 허용하여
+ * 실제 로깅 사용 사례를 지원하면서도 타입 안정성을 유지합니다.
+ */
+export type LogContextValue =
+  | string
+  | number
+  | boolean
+  | null
+  | undefined
+  | unknown
+  | LogContextValue[]
+  | { [key: string]: unknown };
+
+/**
+ * 로그 컨텍스트 타입
+ */
+export type LogContext = Record<string, unknown>;
+
 /**
  * 구조화된 로그 엔트리 인터페이스
  */
@@ -48,7 +73,7 @@ export interface LogEntry {
   /** 서비스명 (예: 'openai', 'telegram', 'deposit') */
   service?: string;
   /** 추가 컨텍스트 정보 */
-  context?: Record<string, any>;
+  context?: LogContext;
   /** 에러 정보 (ERROR/FATAL 레벨용) */
   error?: {
     /** 에러 이름 */
@@ -209,7 +234,7 @@ export class Logger {
   private createEntry(
     level: LogLevel,
     message: string,
-    context?: Record<string, any>,
+    context?: LogContext,
     error?: Error
   ): LogEntry {
     const entry: LogEntry = {
@@ -245,7 +270,7 @@ export class Logger {
    * logger.debug('함수 호출', { functionName: 'processData', args: [1, 2, 3] });
    * ```
    */
-  debug(message: string, context?: Record<string, any>): void {
+  debug(message: string, context?: LogContext): void {
     if (!this.shouldLog(LogLevel.DEBUG)) return;
     this.write(this.createEntry(LogLevel.DEBUG, message, context));
   }
@@ -261,7 +286,7 @@ export class Logger {
    * logger.info('요청 처리 시작', { userId: '123', endpoint: '/api/data' });
    * ```
    */
-  info(message: string, context?: Record<string, any>): void {
+  info(message: string, context?: LogContext): void {
     if (!this.shouldLog(LogLevel.INFO)) return;
     this.write(this.createEntry(LogLevel.INFO, message, context));
   }
@@ -277,7 +302,7 @@ export class Logger {
    * logger.warn('API 응답 지연', { endpoint: '/api/data', responseTime: 5000 });
    * ```
    */
-  warn(message: string, context?: Record<string, any>): void {
+  warn(message: string, context?: LogContext): void {
     if (!this.shouldLog(LogLevel.WARN)) return;
     this.write(this.createEntry(LogLevel.WARN, message, context));
   }
@@ -298,7 +323,7 @@ export class Logger {
    * }
    * ```
    */
-  error(message: string, error?: Error, context?: Record<string, any>): void {
+  error(message: string, error?: Error, context?: LogContext): void {
     if (!this.shouldLog(LogLevel.ERROR)) return;
     this.write(this.createEntry(LogLevel.ERROR, message, context, error));
   }
@@ -315,7 +340,7 @@ export class Logger {
    * logger.fatal('데이터베이스 연결 실패', error, { database: 'main' });
    * ```
    */
-  fatal(message: string, error?: Error, context?: Record<string, any>): void {
+  fatal(message: string, error?: Error, context?: LogContext): void {
     if (!this.shouldLog(LogLevel.FATAL)) return;
     this.write(this.createEntry(LogLevel.FATAL, message, context, error));
   }
@@ -336,7 +361,7 @@ export class Logger {
    * end(); // duration이 자동으로 로그에 포함됨
    * ```
    */
-  startTimer(message?: string, context?: Record<string, any>): () => void {
+  startTimer(message?: string, context?: LogContext): () => void {
     const startTime = Date.now();
     const timerMessage = message || 'Operation completed';
 
@@ -404,7 +429,7 @@ export class Logger {
 export function createLogger(service: string, env?: Partial<Env>): Logger {
   // 환경 감지: 명시적 ENVIRONMENT 변수 또는 프로덕션 감지
   const environment =
-    (env as any)?.ENVIRONMENT === 'production'
+    env && 'ENVIRONMENT' in env && env.ENVIRONMENT === 'production'
       ? 'production'
       : 'development';