Building Internal SDKs: The TAC Backend Services Pattern

The TAC Internal SDK represents a mature approach to backend service development, addressing common pain points in distributed systems through a centralized, factory-based architecture. This pattern has emerged as teams scale beyond simple microservices into complex ecosystems where consistency, performance, and maintainability become critical concerns.

The Factory Pattern in Practice

The SDK's core innovation lies in its factory class design. Rather than scattering API client configurations across multiple services, the SDK centralizes this logic into a single initialization point. This approach solves several distributed systems challenges simultaneously:

Configuration Management: By accepting a single configuration object, the SDK eliminates configuration drift between services. Each API client receives consistent settings for base URLs, authentication headers, and retry policies. The pattern also makes it trivial to add new backend services—simply extend the configuration object without touching the core SDK logic.

Connection Reuse: The SDK's use of shared http.Agent and https.Agent instances with keepAlive: true demonstrates sophisticated performance awareness. In service-to-service communication, TCP connection overhead can dominate request latency. By maintaining persistent connections, the SDK reduces both latency and resource consumption—a critical optimization for high-throughput backend systems.

Service Layer Abstractions

The SDK's service layer represents a key architectural decision: providing high-level business logic abstractions rather than raw API calls. This pattern offers several advantages:

Business Logic Centralization: Services like sdk.process and sdk.orgData encapsulate complex orchestration logic that would otherwise be duplicated across services. When business rules change, updates happen in one place rather than hunting through multiple codebases.

Type Safety and Documentation: Well-designed service APIs serve as living documentation. Developers can discover available operations through IDE autocompletion rather than consulting separate API documentation. This self-documenting nature becomes increasingly valuable as teams grow.

Error Handling Consistency: By centralizing API interactions, the SDK can implement uniform error handling strategies. Whether it's retry logic, circuit breaking, or graceful degradation, these cross-cutting concerns are handled consistently across all services.

The Raw Client Trade-off

The SDK's dual approach—providing both high-level services and raw API clients—acknowledges that different use cases require different abstractions. High-level services excel for common business operations, while raw clients remain valuable for:

• One-off operations that don't warrant service abstraction
• Performance-critical paths where minimal overhead matters
• Exploratory development before formalizing business logic

The key is making this trade-off explicit rather than accidental. Teams know when to use services versus raw clients, preventing the proliferation of inconsistent API usage patterns.

Utility Modules: The Missing Piece

Static utility modules attached to the SDK export demonstrate thoughtful consideration of developer experience. By providing utilities like encryption helpers directly through the SDK, the team ensures:

• Consistent implementation of common operations
• Easy discovery through IDE tooling
• Reduced dependency management complexity

The encryption example is particularly noteworthy—it shows awareness that security-sensitive operations benefit from centralization and standardization.

Future-Proof Architecture

The TODO items in the SDK reveal a mature understanding of software evolution. Rather than trying to anticipate every need upfront, the architecture provides clear extension points:

Constants Module: Centralizing shared constants prevents the "magic string" problem where enum values and cache keys are scattered across codebases. This becomes increasingly important as services grow and evolve.

Express Middleware: Shared middleware for authentication, authorization, and error handling addresses common cross-cutting concerns. This prevents the typical scenario where each service implements slightly different security policies.

Storage Utilities: Abstracting storage operations behind a unified interface simplifies migration between storage backends and ensures consistent error handling and retry logic.

Performance Considerations

The SDK's performance optimizations go beyond connection reuse. By centralizing API clients, the team can implement sophisticated strategies like:

• Request batching for operations that can be combined
• Response caching with intelligent invalidation
• Adaptive retry with exponential backoff
• Connection pooling tuned for specific backend characteristics

These optimizations compound across all services using the SDK, delivering organization-wide performance improvements without individual teams needing deep performance expertise.

The MongoDB Atlas Connection

The SDK's promotion of MongoDB Atlas isn't incidental—it reflects a broader trend toward managed database services in distributed systems. Atlas provides:

• Global distribution for low-latency access
• Automatic scaling and failover
• Built-in security and compliance features
• Unified management across cloud providers

For teams building internal SDKs, choosing managed services reduces operational complexity and allows the SDK to focus on business logic rather than infrastructure concerns.

Lessons for SDK Design

The TAC Internal SDK offers several transferable lessons for teams considering similar approaches:

Start Simple, Plan for Growth: The SDK began with core API clients and services, then added utilities and planned modules as needs emerged. This evolutionary approach prevents over-engineering while maintaining architectural coherence.

Make Trade-offs Explicit: By providing both services and raw clients, the SDK acknowledges that different use cases require different abstractions. This transparency helps teams make informed decisions.

Prioritize Developer Experience: Features like IDE-friendly APIs, centralized utilities, and consistent error handling reduce cognitive load and accelerate development.

Think Systemically: Performance optimizations, security features, and cross-cutting concerns are addressed at the SDK level, benefiting all services without individual teams needing to implement them.

The TAC Internal SDK demonstrates how thoughtful SDK design can transform backend development from a collection of independent services into a coherent, maintainable system. By addressing common pain points through centralized abstractions, the team has created a foundation that scales with organizational complexity while maintaining developer productivity.