Building a Phone Verification System: Architecture Guide for High-Volume Applications

Understanding Phone Verification System Requirements

Before diving into architecture patterns, it's essential to understand the unique challenges and requirements of phone verification systems at scale. These systems must balance real-time performance with data accuracy, security compliance, and global coverage.

Core Architecture Components and Design Patterns

A robust phone verification system requires a carefully designed architecture that separates concerns, enables horizontal scaling, and provides fault tolerance. The following components form the foundation of a scalable phone verification platform.

// High-Level System Architecture
interface PhoneVerificationArchitecture {
  // Edge Layer
  edgeCDN: {
    cloudflareWorkers: CloudflareWorker[];
    fastlyCompute: FastlyCompute@Edge[];
    geographicDistribution: 'global';
  };

  // API Gateway Layer
  apiGateway: {
    kongGateway: KongGatewayConfig;
    rateLimiting: RateLimitConfig;
    authentication: OAuth2Config;
    requestRouting: RoutingConfig;
  };

  // Service Layer (Microservices)
  services: {
    validationService: ValidationMicroservice;
    carrierLookupService: CarrierLookupMicroservice;
    fraudDetectionService: FraudDetectionMicroservice;
    analyticsService: AnalyticsMicroservice;
    complianceService: ComplianceMicroservice;
  };

  // Data Layer
  dataLayer: {
    primaryDatabase: PostgreSQLCluster;
    cacheLayer: RedisCluster;
    searchIndex: ElasticsearchCluster;
    dataWarehouse: Snowflake;
  };

  // Infrastructure Layer
  infrastructure: {
    kubernetesCluster: KubernetesConfig;
    serviceMesh: IstioConfig;
    monitoring: Prometheus + Grafana;
    logging: ELK Stack;
  };
}

Scalability Considerations for High-Volume Processing

Scaling a phone verification system to handle millions of daily requests requires careful consideration of bottlenecks, resource utilization, and performance optimization strategies.

// Kubernetes Horizontal Pod Autoscaler Configuration
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: phone-validation-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: phone-validation-service
  minReplicas: 10
  maxReplicas: 1000
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80
  - type: Pods
    pods:
      metric:
        name: requests_per_second
      target:
        type: AverageValue
        averageValue: "100"
  behavior:
    scaleDown:
      stabilizationWindowSeconds: 300
      policies:
      - type: Percent
        value: 10
        periodSeconds: 60
    scaleUp:
      stabilizationWindowSeconds: 60
      policies:
      - type: Percent
        value: 100
        periodSeconds: 15
      - type: Pods
        value: 10
        periodSeconds: 15
      selectPolicy: Max

Data Management and Caching Strategies

Efficient data management is critical for phone verification systems that must process millions of requests while maintaining data accuracy and providing real-time responses.

// Redis Cluster Configuration for High-Performance Caching
const redisCluster = new Redis.Cluster([
  { host: 'redis-node-1.example.com', port: 6379 },
  { host: 'redis-node-2.example.com', port: 6379 },
  { host: 'redis-node-3.example.com', port: 6379 },
  { host: 'redis-node-4.example.com', port: 6379 },
  { host: 'redis-node-5.example.com', port: 6379 },
  { host: 'redis-node-6.example.com', port: 6379 }
], {
  enableReadyCheck: false,
  redisOptions: {
    password: process.env.REDIS_PASSWORD,
    tls: {
      rejectUnauthorized: false
    }
  },
  maxRetriesPerRequest: 3,
  retryDelayOnFailover: 100,
  lazyConnect: true
});

// Phone Verification Cache Strategy
class PhoneVerificationCache {
  constructor(redisClient) {
    this.redis = redisClient;
    this.cacheConfig = {
      validationCache: { ttl: 3600 },      // 1 hour
      carrierCache: { ttl: 86400 },        // 24 hours
      riskScoreCache: { ttl: 1800 },       // 30 minutes
      analyticsCache: { ttl: 300 }         // 5 minutes
    };
  }

  async getValidationResult(phoneNumber) {
    const cacheKey = `validation:${phoneNumber}`;
    const cached = await this.redis.get(cacheKey);

    if (cached) {
      const result = JSON.parse(cached);
      result.fromCache = true;
      return result;
    }

    return null;
  }

  async setValidationResult(phoneNumber, result) {
    const cacheKey = `validation:${phoneNumber}`;
    const value = JSON.stringify(result);
    const ttl = this.cacheConfig.validationCache.ttl;

    await this.redis.setex(cacheKey, ttl, value);
  }

  async invalidateCache(phoneNumber) {
    const patterns = [
      `validation:${phoneNumber}`,
      `carrier:${phoneNumber}`,
      `risk:${phoneNumber}`
    ];

    const pipeline = this.redis.pipeline();
    patterns.forEach(pattern => pipeline.del(pattern));
    await pipeline.exec();
  }

  async batchValidationResults(phoneNumbers) {
    const pipeline = this.redis.pipeline();
    const cacheKeys = phoneNumbers.map(phone => `validation:${phone}`);

    cacheKeys.forEach(key => pipeline.get(key));
    const results = await pipeline.exec();

    return phoneNumbers.map((phone, index) => {
      const [err, cached] = results[index];
      if (cached) {
        return {
          phoneNumber: phone,
          result: JSON.parse(cached),
          fromCache: true
        };
      }
      return { phoneNumber: phone, fromCache: false };
    });
  }
}

API Design and Integration Patterns

Well-designed APIs are crucial for phone verification systems that need to integrate with diverse client applications while maintaining performance and security.

// Phone Verification API Specification
// OpenAPI 3.0 Specification

openapi: 3.0.3
info:
  title: Phone Verification API
  version: 2.0.0
  description: Enterprise-grade phone verification and validation services

servers:
  - url: https://api.phone-check.app/v2
    description: Production server
  - url: https://staging-api.phone-check.app/v2
    description: Staging server

paths:
  /verify:
    post:
      summary: Validate phone number
      description: Comprehensive phone number validation with carrier lookup
      operationId: validatePhoneNumber
      tags:
        - Phone Verification
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - phone_number
              properties:
                phone_number:
                  type: string
                  pattern: '^\\+?[1-9]\\d{1,14}$'
                  example: "+1234567890"
                  description: Phone number in E.164 format
                country_code:
                  type: string
                  length: 2
                  example: "US"
                  description: ISO 3166-1 alpha-2 country code
                verification_type:
                  type: string
                  enum: [basic, standard, premium]
                  default: standard
                  description: Level of verification to perform
                include_carrier_info:
                  type: boolean
                  default: false
                  description: Include detailed carrier information
                risk_assessment:
                  type: boolean
                  default: false
                  description: Perform fraud risk assessment
      responses:
        '200':
          description: Phone verification completed successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  request_id:
                    type: string
                    format: uuid
                    description: Unique request identifier
                  phone_number:
                    type: string
                    description: Original phone number
                  is_valid:
                    type: boolean
                    description: Phone number validity status
                  phone_type:
                    type: string
                    enum: [mobile, landline, voip, toll_free, premium]
                    description: Detected phone number type
                  carrier:
                    type: object
                    properties:
                      name:
                        type: string
                        description: Carrier name
                      network_type:
                        type: string
                        description: Network type (GSM, CDMA, etc.)
                      country:
                        type: string
                        description: Carrier country
                  location:
                    type: object
                    properties:
                      country:
                        type: string
                        description: Phone number country
                      region:
                        type: string
                        description: Geographic region
                      timezone:
                        type: string
                        description: Timezone
                  risk_score:
                    type: object
                    properties:
                      score:
                        type: number
                        minimum: 0
                        maximum: 100
                        description: Risk score (0=low risk, 100=high risk)
                      factors:
                        type: array
                        items:
                          type: string
                        description: Risk factors identified
                  response_time_ms:
                    type: number
                    description: API response time in milliseconds
                  cached:
                    type: boolean
                    description: Whether response was served from cache

  /verify/batch:
    post:
      summary: Batch phone number verification
      description: Verify multiple phone numbers in a single request
      operationId: batchValidatePhoneNumbers
      tags:
        - Phone Verification
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - phone_numbers
              properties:
                phone_numbers:
                  type: array
                  items:
                    type: string
                  maxItems: 1000
                  description: Array of phone numbers to verify
                verification_type:
                  type: string
                  enum: [basic, standard, premium]
                  default: standard
                callback_url:
                  type: string
                  format: uri
                  description: Webhook URL for batch completion notification
      responses:
        '200':
          description: Batch verification initiated
          content:
            application/json:
              schema:
                type: object
                properties:
                  batch_id:
                    type: string
                    format: uuid
                    description: Unique batch identifier
                  status:
                    type: string
                    enum: [processing, completed, failed]
                  total_count:
                    type: integer
                    description: Total number of phone numbers in batch
                  estimated_completion:
                    type: string
                    format: date-time
                    description: Estimated completion time

  /analytics:
    get:
      summary: Get verification analytics
      description: Retrieve analytics and usage statistics
      operationId: getVerificationAnalytics
      tags:
        - Analytics
      parameters:
        - name: date_range
          in: query
          schema:
            type: string
            enum: [today, yesterday, last_7_days, last_30_days, custom]
          default: last_30_days
        - name: start_date
          in: query
          schema:
            type: string
            format: date
          description: Start date for custom range
        - name: end_date
          in: query
          schema:
            type: string
            format: date
          description: End date for custom range
        - name: group_by
          in: query
          schema:
            type: string
            enum: [day, hour, country, carrier, phone_type]
          default: day
      responses:
        '200':
          description: Analytics data retrieved successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  total_requests:
                    type: integer
                  success_rate:
                    type: number
                    format: percentage
                  average_response_time:
                    type: number
                  top_countries:
                    type: array
                    items:
                      type: object
                      properties:
                        country:
                          type: string
                        count:
                          type: integer
                  phone_type_distribution:
                    type: object
                    additionalProperties:
                      type: integer
                  error_distribution:
                    type: object
                    additionalProperties:
                      type: integer

Performance Optimization Techniques

Achieving sub-50ms response times at scale requires optimization across all system layers, from network infrastructure to application code.

// Performance Monitoring Implementation
class PerformanceMonitor {
  constructor(metricsCollector) {
    this.metrics = metricsCollector;
    this.thresholds = {
      responseTime: 50,    // ms
      errorRate: 0.01,     // 1%
      throughput: 1000     // requests/second
    };
  }

  async measureRequestValidation(handler) {
    return async (req, res) => {
      const startTime = process.hrtime.bigint();
      const requestId = this.generateRequestId();

      try {
        // Add request metadata
        req.requestId = requestId;
        req.startTime = startTime;

        // Execute the handler
        const result = await handler(req, res);

        // Calculate response time
        const endTime = process.hrtime.bigint();
        const responseTime = Number(endTime - startTime) / 1000000; // Convert to ms

        // Record metrics
        await this.recordMetrics({
          requestId,
          responseTime,
          status: 'success',
          endpoint: req.path,
          method: req.method,
          userAgent: req.headers['user-agent'],
          ipAddress: req.ip
        });

        // Add performance headers
        res.setHeader('X-Response-Time', `${responseTime.toFixed(2)}ms`);
        res.setHeader('X-Request-ID', requestId);

        return result;

      } catch (error) {
        const endTime = process.hrtime.bigint();
        const responseTime = Number(endTime - startTime) / 1000000;

        // Record error metrics
        await this.recordMetrics({
          requestId,
          responseTime,
          status: 'error',
          error: error.message,
          endpoint: req.path,
          method: req.method
        });

        throw error;
      }
    };
  }

  async recordMetrics(data) {
    const metric = {
      timestamp: new Date().toISOString(),
      service: 'phone-verification',
      ...data
    };

    // Send to monitoring system
    await this.metrics.record(metric);

    // Check for performance alerts
    this.checkPerformanceAlerts(metric);
  }

  checkPerformanceAlerts(metric) {
    if (metric.responseTime > this.thresholds.responseTime) {
      this.triggerAlert({
        type: 'slow_response',
        severity: 'warning',
        message: `Response time ${metric.responseTime}ms exceeds threshold ${this.thresholds.responseTime}ms`,
        requestId: metric.requestId,
        endpoint: metric.endpoint
      });
    }

    // Update running averages
    this.updatePerformanceMetrics(metric);
  }

  updatePerformanceMetrics(metric) {
    const key = `${metric.method}:${metric.endpoint}`;

    if (!this.performanceData[key]) {
      this.performanceData[key] = {
        requestCount: 0,
        totalResponseTime: 0,
        errorCount: 0,
        minResponseTime: Infinity,
        maxResponseTime: 0
      };
    }

    const stats = this.performanceData[key];
    stats.requestCount++;
    stats.totalResponseTime += metric.responseTime;

    if (metric.status === 'error') {
      stats.errorCount++;
    }

    stats.minResponseTime = Math.min(stats.minResponseTime, metric.responseTime);
    stats.maxResponseTime = Math.max(stats.maxResponseTime, metric.responseTime);

    // Calculate averages
    stats.averageResponseTime = stats.totalResponseTime / stats.requestCount;
    stats.errorRate = stats.errorCount / stats.requestCount;
  }

  getPerformanceReport() {
    return {
      generatedAt: new Date().toISOString(),
      summary: {
        totalRequests: Object.values(this.performanceData)
          .reduce((sum, stats) => sum + stats.requestCount, 0),
        averageResponseTime: this.calculateGlobalAverage(),
        overallErrorRate: this.calculateGlobalErrorRate()
      },
      endpoints: this.performanceData
    };
  }
}

// Database Query Optimization
class QueryOptimizer {
  constructor(database) {
    this.db = database;
    this.queryCache = new Map();
    this.slowQueryThreshold = 100; // ms
  }

  async optimizedPhoneValidation(phoneNumber) {
    const cacheKey = `phone_validation:${phoneNumber}`;

    // Check cache first
    if (this.queryCache.has(cacheKey)) {
      const cached = this.queryCache.get(cacheKey);
      if (Date.now() - cached.timestamp < 3600000) { // 1 hour
        return cached.data;
      }
    }

    const startTime = Date.now();

    // Optimized database query with indexes
    const query = `
      SELECT
        p.phone_number,
        p.country_code,
        p.is_valid,
        p.phone_type,
        c.name as carrier_name,
        c.network_type,
        l.country,
        l.region,
        l.timezone
      FROM phone_numbers p
      LEFT JOIN carriers c ON p.carrier_id = c.id
      LEFT JOIN locations l ON p.location_id = l.id
      WHERE p.phone_number = $1
      AND p.updated_at > NOW() - INTERVAL '24 hours'
    `;

    const result = await this.db.query(query, [phoneNumber]);
    const queryTime = Date.now() - startTime;

    // Log slow queries
    if (queryTime > this.slowQueryThreshold) {
      console.warn(`Slow query detected: ${queryTime}ms for phone ${phoneNumber}`);
    }

    // Cache result
    this.queryCache.set(cacheKey, {
      data: result.rows[0] || null,
      timestamp: Date.now()
    });

    return result.rows[0] || null;
  }

  async batchPhoneValidation(phoneNumbers) {
    // Use IN clause for batch operations
    const query = `
      SELECT
        p.phone_number,
        p.country_code,
        p.is_valid,
        p.phone_type,
        c.name as carrier_name,
        c.network_type,
        l.country,
        l.region,
        l.timezone
      FROM phone_numbers p
      LEFT JOIN carriers c ON p.carrier_id = c.id
      LEFT JOIN locations l ON p.location_id = l.id
      WHERE p.phone_number = ANY($1)
      AND p.updated_at > NOW() - INTERVAL '24 hours'
    `;

    const result = await this.db.query(query, [phoneNumbers]);

    // Create lookup map for efficient access
    const resultMap = new Map();
    result.rows.forEach(row => {
      resultMap.set(row.phone_number, row);
    });

    return phoneNumbers.map(phone => resultMap.get(phone) || null);
  }
}

Security and Compliance Considerations

Security is paramount for phone verification systems that handle sensitive personal data and must comply with global privacy regulations.

// Security Middleware Implementation
class SecurityMiddleware {
  constructor(config) {
    this.config = config;
    this.rateLimiter = new RateLimiter();
    this.encryptionService = new EncryptionService();
    this.auditLogger = new AuditLogger();
  }

  async securityMiddleware(req, res, next) {
    try {
      // 1. Rate limiting
      const rateLimitResult = await this.rateLimiter.checkLimit(req);
      if (!rateLimitResult.allowed) {
        return res.status(429).json({
          error: 'Rate limit exceeded',
          retryAfter: rateLimitResult.retryAfter
        });
      }

      // 2. Authentication validation
      const authResult = await this.validateAuthentication(req);
      if (!authResult.valid) {
        await this.logSecurityEvent({
          type: 'authentication_failure',
          ip: req.ip,
          userAgent: req.headers['user-agent'],
          reason: authResult.reason
        });
        return res.status(401).json({ error: 'Authentication failed' });
      }

      // 3. Input validation and sanitization
      const validationResult = await this.validateInput(req.body);
      if (!validationResult.valid) {
        return res.status(400).json({
          error: 'Invalid input',
          details: validationResult.errors
        });
      }

      // 4. Data encryption for sensitive fields
      if (req.body.phone_number) {
        req.body.encrypted_phone = await this.encryptionService.encrypt(req.body.phone_number);
        delete req.body.phone_number;
      }

      // 5. Add security headers
      this.addSecurityHeaders(res);

      // 6. Log the request for audit trail
      await this.auditLogger.logRequest({
        requestId: req.id,
        userId: authResult.userId,
        endpoint: req.path,
        method: req.method,
        ip: req.ip,
        timestamp: new Date()
      });

      next();
    } catch (error) {
      console.error('Security middleware error:', error);
      res.status(500).json({ error: 'Internal security error' });
    }
  }

  async validateAuthentication(req) {
    const authHeader = req.headers.authorization;

    if (!authHeader || !authHeader.startsWith('Bearer ')) {
      return { valid: false, reason: 'Missing or invalid authorization header' };
    }

    const token = authHeader.substring(7);

    try {
      // Verify JWT token
      const decoded = jwt.verify(token, process.env.JWT_SECRET);

      // Check if token is not expired
      if (decoded.exp < Date.now() / 1000) {
        return { valid: false, reason: 'Token expired' };
      }

      // Validate user permissions
      const user = await this.getUserById(decoded.userId);
      if (!user || !user.isActive) {
        return { valid: false, reason: 'User not found or inactive' };
      }

      // Check API key permissions
      const apiKey = await this.validateApiKey(req.headers['x-api-key']);
      if (!apiKey || !apiKey.isValid) {
        return { valid: false, reason: 'Invalid API key' };
      }

      return {
        valid: true,
        userId: user.id,
        permissions: user.permissions,
        apiKeyId: apiKey.id
      };
    } catch (error) {
      return { valid: false, reason: 'Token verification failed' };
    }
  }

  addSecurityHeaders(res) {
    // Security headers
    res.setHeader('X-Content-Type-Options', 'nosniff');
    res.setHeader('X-Frame-Options', 'DENY');
    res.setHeader('X-XSS-Protection', '1; mode=block');
    res.setHeader('Strict-Transport-Security', 'max-age=31536000; includeSubDomains');
    res.setHeader('Content-Security-Policy', "default-src 'self'");
    res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');

    // CORS headers
    res.setHeader('Access-Control-Allow-Origin', this.config.allowedOrigins.join(','));
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization, X-API-Key');
    res.setHeader('Access-Control-Max-Age', '86400');
  }

  async logSecurityEvent(event) {
    const securityEvent = {
      ...event,
      timestamp: new Date(),
      service: 'phone-verification-api',
      severity: this.determineSeverity(event.type)
    };

    await this.auditLogger.logSecurityEvent(securityEvent);

    // Trigger alerts for high-severity events
    if (securityEvent.severity === 'high') {
      await this.triggerSecurityAlert(securityEvent);
    }
  }
}

// GDPR/CCPA Compliance Implementation
class ComplianceManager {
  constructor() {
    this.dataRetention = new DataRetentionManager();
    this.consentManager = new ConsentManager();
    this.auditLogger = new AuditLogger();
  }

  async processPhoneVerification(phoneNumber, userId, context) {
    // 1. Check for valid consent
    const consent = await this.consentManager.getValidConsent(userId, 'phone_verification');
    if (!consent) {
      throw new Error('Insufficient consent for phone verification');
    }

    // 2. Log processing purpose
    await this.auditLogger.logProcessing({
      userId,
      dataType: 'phone_number',
      purpose: context.purpose,
      lawfulBasis: consent.lawfulBasis,
      timestamp: new Date()
    });

    // 3. Process with data minimization
    const result = await this.performVerification(phoneNumber, {
      minimizeData: true,
      purpose: context.purpose
    });

    // 4. Set retention policy
    await this.dataRetention.scheduleDeletion({
      userId,
      dataType: 'phone_verification_result',
      retentionPeriod: this.calculateRetentionPeriod(context.purpose),
      dataId: result.id
    });

    return result;
  }

  async handleDataSubjectRequest(request) {
    const { userId, requestType, requestId } = request;

    await this.auditLogger.logDataSubjectRequest({
      requestId,
      userId,
      requestType,
      timestamp: new Date()
    });

    switch (requestType) {
      case 'access':
        return await this.provideDataAccess(userId);
      case 'deletion':
        return await this.deleteUserData(userId);
      case 'rectification':
        return await this.rectifyData(userId, request.corrections);
      case 'portability':
        return await this.exportUserData(userId);
      default:
        throw new Error('Unsupported request type');
    }
  }

  calculateRetentionPeriod(purpose) {
    const retentionPeriods = {
      'fraud_prevention': 2555,  // 7 years
      'service_delivery': 1825,  // 5 years
      'marketing': 730,          // 2 years
      'analytics': 365,          // 1 year
      'compliance': 2555         // 7 years
    };

    return retentionPeriods[purpose] || 365;
  }
}

Monitoring and Observability Best Practices

Comprehensive monitoring and observability are essential for maintaining system reliability, performance, and security in high-volume phone verification systems.

Deployment and Infrastructure Patterns

Modern deployment patterns ensure reliable, scalable, and maintainable phone verification systems with continuous delivery and zero-downtime deployments.

// Kubernetes Deployment for Phone Verification Service
apiVersion: apps/v1
kind: Deployment
metadata:
  name: phone-validation-service
  labels:
    app: phone-validation
    version: v2
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 0
      maxSurge: 1
  selector:
    matchLabels:
      app: phone-validation
  template:
    metadata:
      labels:
        app: phone-validation
        version: v2
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "9090"
        prometheus.io/path: "/metrics"
    spec:
      containers:
      - name: phone-validation
        image: phone-check/phone-validation:v2.1.0
        ports:
        - containerPort: 8080
          name: http
        - containerPort: 9090
          name: metrics
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: database-secret
              key: url
        - name: REDIS_URL
          valueFrom:
            secretKeyRef:
              name: redis-secret
              key: url
        - name: JWT_SECRET
          valueFrom:
            secretKeyRef:
              name: jwt-secret
              key: secret
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
          failureThreshold: 3
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
          timeoutSeconds: 3
          failureThreshold: 3
        securityContext:
          runAsNonRoot: true
          runAsUser: 1000
          allowPrivilegeEscalation: false
          readOnlyRootFilesystem: true
          capabilities:
            drop:
            - ALL
        volumeMounts:
        - name: tmp
          mountPath: /tmp
        - name: cache
          mountPath: /app/cache
      volumes:
      - name: tmp
        emptyDir: {}
      - name: cache
        emptyDir:
          sizeLimit: 100Mi
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 100
            podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: app
                  operator: In
                  values:
                  - phone-validation
              topologyKey: kubernetes.io/hostname

---
apiVersion: v1
kind: Service
metadata:
  name: phone-validation-service
  labels:
    app: phone-validation
spec:
  selector:
    app: phone-validation
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP
  - name: metrics
    port: 9090
    targetPort: 9090
    protocol: TCP
  type: ClusterIP

---
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: phone-validation-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: phone-validation-service
  minReplicas: 3
  maxReplicas: 50
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80
  - type: Pods
    pods:
      metric:
        name: http_requests_per_second
      target:
        type: AverageValue
        averageValue: "100"
  behavior:
    scaleDown:
      stabilizationWindowSeconds: 300
      policies:
      - type: Percent
        value: 10
        periodSeconds: 60
    scaleUp:
      stabilizationWindowSeconds: 60
      policies:
      - type: Percent
        value: 100
        periodSeconds: 15
      - type: Pods
        value: 5
        periodSeconds: 15
      selectPolicy: Max

Case Study: 10M+ Daily Verification Requests Architecture

Let's examine a real-world implementation of a phone verification system handling over 10 million daily requests with 99.99% availability and sub-50ms response times.

Implementation Roadmap and Best Practices

Follow this structured approach to implement a scalable phone verification system, from initial development to production deployment at scale.