Building Large-Scale Client Applications: REST API Integration and Real-Time Data Synchronization

The Foundation

My journey as a professional developer began at Azma Data Structure, where I spent three years (2018-2021) building large-scale client applications. This role was foundational—it taught me the fundamentals of building production applications that integrate with complex backend systems.

The Challenge

At Azma, I worked on client applications that needed to:

Key Responsibilities

1. REST API Integration

I built robust integration layers that handled:

// API client with retry logic
class ApiClient {
  private baseURL: string;
  private token: string | null = null;
  
  async request(
    endpoint: string,
    options: RequestInit = {}
  ): Promise {
    const maxRetries = 3;
    let lastError: Error;
    
    for (let attempt = 0; attempt < maxRetries; attempt++) {
      try {
        const response = await fetch(${this.baseURL}${endpoint}, {
          ...options,
          headers: {
            'Authorization': Bearer ${this.token},
            'Content-Type': 'application/json',
            ...options.headers
          }
        });
        
        if (!response.ok) {
          if (response.status === 401) {
            await this.refreshToken();
            continue; // Retry with new token
          }
          throw new Error(API Error: ${response.status});
        }
        
        return await response.json();
        
      } catch (error) {
        lastError = error;
        
        // Exponential backoff
        if (attempt < maxRetries - 1) {
          await this.delay(Math.pow(2, attempt) * 1000);
        }
      }
    }
    
    throw lastError!;
  }
  
  private async refreshToken() {
    const response = await fetch(${this.baseURL}/auth/refresh, {
      method: 'POST',
      body: JSON.stringify({ refreshToken: this.refreshToken })
    });
    
    const data = await response.json();
    this.token = data.accessToken;
  }
}

2. Real-Time Data Synchronization

I implemented real-time synchronization mechanisms that kept client data in sync with the backend:

// Real-time sync service
class DataSyncService {
  private apiClient: ApiClient;
  private syncInterval: number = 30000; // 30 seconds
  private lastSyncTime: number = 0;
  
  async syncData() {
    try {
      // Fetch updates since last sync
      const updates = await this.apiClient.request(
        /api/sync?since=${this.lastSyncTime}
      );
      
      // Apply updates to local store
      for (const update of updates) {
        await this.applyUpdate(update);
      }
      
      this.lastSyncTime = Date.now();
      
    } catch (error) {
      console.error('Sync failed', error);
      // Queue for retry
      this.queueSync();
    }
  }
  
  private async applyUpdate(update: Update) {
    switch (update.type) {
      case 'create':
        await this.localStore.create(update.data);
        break;
      case 'update':
        await this.localStore.update(update.id, update.data);
        break;
      case 'delete':
        await this.localStore.delete(update.id);
        break;
    }
  }
  
  startAutoSync() {
    setInterval(() => this.syncData(), this.syncInterval);
  }
}

3. Performance Optimization

I focused on optimizing application performance:

// Optimized list rendering with virtual scrolling
class VirtualList {
  private items: T[] = [];
  private visibleRange: { start: number; end: number } = { start: 0, end: 50 };
  
  render() {
    const visibleItems = this.items.slice(
      this.visibleRange.start,
      this.visibleRange.end
    );
    
    return visibleItems.map((item, index) => (
              key={this.visibleRange.start + index}
        data={item}
      />
    ));
  }
  
  onScroll(scrollTop: number, containerHeight: number) {
    const itemHeight = 50;
    const start = Math.floor(scrollTop / itemHeight);
    const end = start + Math.ceil(containerHeight / itemHeight);
    
    this.visibleRange = { start, end };
    this.render();
  }
}

Lessons Learned

Impact

During my time at Azma:

Conclusion

My time at Azma Data Structure was foundational. It taught me the fundamentals of building production applications, integrating with backend systems, and optimizing for performance. The experience provided the base upon which I built more complex systems in later roles.

The skills I developed—from API integration to performance optimization—continue to be relevant in every project I work on.

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This foundational experience shaped my approach to building client applications throughout my career.