SDK Library Development for SaaS Integration
Imagine you launch a SaaS product and your first clients complain that integrating with your API takes weeks. They manually send HTTP requests, handle errors, and write their own pagination. The entry barrier is too high. We solve this by developing a client SDK — a ready-to-use library that reduces integration time to hours. Our experience: 7+ years building SDKs for B2B SaaS, 50+ successful projects. While in-house development can cost $10,000–$20,000 in developer time alone, our turnkey SDK starts at $1,500, saving you up to $18,500.
How an SDK Speeds Up Integration
An SDK encapsulates typical tasks: authorization, retries with exponential backoff, pagination, webhook verification. The developer just installs the package and calls methods. Instead of 500 lines of code — 5 lines. This cuts time-to-market (TTM) by 80%.
Why Order SDK from Professionals?
In-house SDK development requires time and expertise: proper retry logic, avoiding race conditions, maintaining backward compatibility. We’ve done it dozens of times. We use proven patterns: Repository, BFF, typed responses. We guarantee stability and full documentation. Below is a quality comparison table.
| Parameter | Our SDK | In-House Development |
|---|---|---|
| Typing | Full (TypeScript) | Fragmented |
| Retries | Exponential backoff with jitter | Basic or none |
| Pagination | Cursor-based auto-paging | Often offset/limit |
| Webhooks | HMAC verification via timingSafeEqual | Often missing |
| Documentation | README with examples and tests | Minimal |
What’s Included in SDK Work (Deliverables)
- API and OpenAPI analysis — define resources and public interface.
- Typed HTTP client in TypeScript with retries and timeouts.
- Pagination (cursor-based), webhook verification, and error handling.
- Tests (vitest/jest) with 80% coverage of the public API.
- Build (tsup) and publication to npm with ESM and CJS support.
- Documentation: README with examples, CHANGELOG, migration guide.
- Team consultation (up to 2 hours) and 1-month bug fix guarantee.
SDK Project Structure
my-api-sdk/
src/
client.ts # Main HTTP client
resources/
users.ts # Resource: users
projects.ts # Resource: projects
webhooks.ts # Webhook verification
types/
index.ts # All public types
responses.ts # API response types
errors.ts # Custom errors
retry.ts # Retry logic
pagination.ts # Pager for lists
tests/
client.test.ts
dist/ # Compiled JS + types
package.json
tsconfig.json
README.md
HTTP Client
// src/client.ts
export interface MyApiConfig {
apiKey: string;
baseUrl?: string;
timeout?: number;
maxRetries?: number;
}
export class MyApiError extends Error {
constructor(
message: string,
public readonly statusCode: number,
public readonly code: string,
public readonly requestId: string
) {
super(message);
this.name = 'MyApiError';
}
}
export class MyApiClient {
private readonly baseUrl: string;
private readonly apiKey: string;
private readonly timeout: number;
private readonly maxRetries: number;
// Resources
public readonly users: UsersResource;
public readonly projects: ProjectsResource;
public readonly webhooks: WebhooksResource;
constructor(config: MyApiConfig) {
this.baseUrl = config.baseUrl ?? 'https://api.myproduct.com/v1';
this.apiKey = config.apiKey;
this.timeout = config.timeout ?? 30_000;
this.maxRetries = config.maxRetries ?? 3;
this.users = new UsersResource(this);
this.projects = new ProjectsResource(this);
this.webhooks = new WebhooksResource(this);
}
async request<T>(
method: string,
path: string,
options: RequestOptions = {}
): Promise<T> {
const url = `${this.baseUrl}${path}`;
const headers: Record<string, string> = {
'Authorization': `Bearer ${this.apiKey}`,
'Content-Type': 'application/json',
'User-Agent': `myapi-sdk-node/${SDK_VERSION}`,
'X-SDK-Version': SDK_VERSION,
};
let lastError: Error | undefined;
for (let attempt = 0; attempt <= this.maxRetries; attempt++) {
if (attempt > 0) {
// Exponential backoff: 1s, 2s, 4s
await new Promise(resolve => setTimeout(resolve, 2 ** (attempt - 1) * 1000));
}
try {
const controller = new AbortController();
const timeoutId = setTimeout(() => controller.abort(), this.timeout);
const response = await fetch(url, {
method,
headers,
body: options.body ? JSON.stringify(options.body) : undefined,
signal: controller.signal,
});
clearTimeout(timeoutId);
const requestId = response.headers.get('x-request-id') ?? 'unknown';
if (!response.ok) {
const error = await response.json().catch(() => ({}));
// Don't retry client errors
if (response.status < 500) {
throw new MyApiError(
error.message ?? 'API Error',
response.status,
error.code ?? 'UNKNOWN',
requestId
);
}
lastError = new MyApiError(
error.message ?? 'Server Error',
response.status,
error.code ?? 'SERVER_ERROR',
requestId
);
continue;
}
if (response.status === 204) return undefined as T;
return response.json();
} catch (error) {
if (error instanceof MyApiError) throw error;
lastError = error as Error;
}
}
throw lastError;
}
}
Resource with Pagination
// src/resources/projects.ts
export interface Project {
id: string;
name: string;
status: 'active' | 'archived';
createdAt: string;
}
export interface ListProjectsParams {
limit?: number;
cursor?: string;
status?: 'active' | 'archived';
}
export interface PaginatedResponse<T> {
data: T[];
nextCursor?: string;
hasMore: boolean;
total: number;
}
export class ProjectsResource {
constructor(private client: MyApiClient) {}
async list(params: ListProjectsParams = {}): Promise<PaginatedResponse<Project>> {
const query = new URLSearchParams();
if (params.limit) query.set('limit', params.limit.toString());
if (params.cursor) query.set('cursor', params.cursor);
if (params.status) query.set('status', params.status);
return this.client.request('GET', `/projects?${query}`);
}
// Auto-paging iterator
async *listAll(params: Omit<ListProjectsParams, 'cursor'> = {}): AsyncIterable<Project> {
let cursor: string | undefined;
do {
const page = await this.list({ ...params, cursor, limit: params.limit ?? 100 });
yield* page.data;
cursor = page.nextCursor;
} while (cursor);
}
async create(data: { name: string; description?: string }): Promise<Project> {
return this.client.request('POST', '/projects', { body: data });
}
async get(id: string): Promise<Project> {
return this.client.request('GET', `/projects/${id}`);
}
async update(id: string, data: Partial<Pick<Project, 'name' | 'status'>>): Promise<Project> {
return this.client.request('PATCH', `/projects/${id}`, { body: data });
}
async delete(id: string): Promise<void> {
return this.client.request('DELETE', `/projects/${id}`);
}
}
Webhook Verification
// src/resources/webhooks.ts
import { createHmac, timingSafeEqual } from 'crypto';
export class WebhooksResource {
constructor(private client: MyApiClient) {}
verify(payload: string | Buffer, signature: string, secret: string): boolean {
const expectedSignature = 'sha256=' + createHmac('sha256', secret)
.update(payload)
.digest('hex');
const sigBuffer = Buffer.from(signature);
const expectedBuffer = Buffer.from(expectedSignature);
if (sigBuffer.length !== expectedBuffer.length) return false;
return timingSafeEqual(sigBuffer, expectedBuffer);
}
constructEvent(
payload: string,
signature: string,
secret: string
): WebhookEvent {
if (!this.verify(payload, signature, secret)) {
throw new Error('Invalid webhook signature');
}
return JSON.parse(payload);
}
}
Common Pitfalls in DIY SDK Implementation
- Incorrect rate limiting handling — clients get blocked on the API side.
- Lack of retries with backoff — transient errors break integration.
- Inconsistent pagination — not all endpoints support cursor.
- Webhook vulnerability — signatures not verified, events can be spoofed.
Comparison: In-House vs Turnkey SDK
| Feature | In-House | Turnkey SDK |
|---|---|---|
| Time (one developer) | 2–4 weeks | 3–5 days |
| Risk of errors (retries, race conditions) | High | Minimal (guaranteed) |
| Documentation and tests | Partial | Complete |
| Maintenance and updates | Your resource | Our support |
| Cost | $10,000–$20,000 | Starting at $1,500 |
How We Do It: Real Case
A client — a SaaS project management platform. Their REST API was used by 10 partners, each writing their own integration. We developed a TypeScript SDK in 4 days and published it to npm. Integration time for partners dropped from 3 days to 2 hours. Partners just installed the package and called methods. Retrospectively, clients praised the reduced TTM and fewer bugs. — Client CTO, project management platform
Our Process
- Analysis: study your API, OpenAPI spec, SDK requirements.
- Design: define resource structure, interfaces, public API.
- Implementation: write client, resources, pagination, webhooks, tests.
- Build and publish: set up tsup, prepare npm package.
- Delivery: source code, documentation, consultation.
Development of a TypeScript SDK with auto-retries, pagination, and npm publication takes 3–5 business days. Implementing an SDK simplifies integrations with your SaaS application many times faster than the DIY approach.
What’s Included in SDK Work
According to industry reports, 63% of developers say SDK quality is a key factor when choosing a platform. We keep that in mind with every implementation.
- Analysis of your API and OpenAPI spec — define resources and public interface.
- Development of a typed HTTP client in TypeScript with retries and timeouts.
- Implementation of pagination (cursor-based), webhook verification, and error handling.
- Tests (vitest/jest) with 80% coverage of the public API.
- Build (tsup) and publish to npm with ESM and CJS support.
- Documentation: README with examples, CHANGELOG, migration guide.
- Consultation for the client’s team on integration (up to 2 hours).
Pricing for a basic TypeScript SDK for REST API starts from $1,500. SDKs with GraphQL, streaming, or OAuth 2.0 are priced accordingly. We provide an exact estimate within one business day after auditing your API.
Contact us — we’ll evaluate your project and propose the optimal solution. Order a turnkey SDK and accelerate your product’s integration.