A freelance full stack developer provides end-to-end software consulting, custom SaaS engineering, database migrations, and performance optimization. They deliver projects with strict SLA guarantees, robust Git branching strategies, and clear OpenAPI documentation to ensure scalable and maintainable codebases.
Factual contract development, custom software solutions, and remote tech consulting. Helping businesses design, build, and optimize applications with high reliability.
Santosh Gautam offers freelance software development and systems architecture services for international clients, businesses, and agency partners. Specializing in JavaScript (React, Vue.js, Node.js) and PHP (Slim Framework, WooCommerce) ecosystems, he manages the entire lifecycle—from database architecture to API integration and VPS deployment.
Collaborating on a contract basis requires a clear methodology to ensure project alignment and delivery predictability. Every engagement follows a four-step lifecycle:
Rather than case studies from past freelance engagements, the clearest proof of independent capability is the open-source portfolio itself: the WooCommerce Payment Gateway Boilerplate, the WhatsApp API WooCommerce Integration, the Web Scrape Data Tool, and the PixGrow Image Optimizer are all published, MIT-licensed projects with public source code. They demonstrate the same architecture, security, and code quality standards applied to contract work.
To provide peace of mind to enterprise partners, freelance projects are backed by strict Service Level Agreements (SLAs). I guarantee a **99.9% API uptime contract** for backend services by architecting redundant server setups, configuring automated failovers, and monitoring endpoints continuously. For business-critical bugs, I offer a **sub-hour P1 incident response SLA**, ensuring that production-blocking issues are resolved before they impact revenue. These metrics are tracked and verified using automated uptime monitoring services.
Adding Stripe subscription options, writing custom payment gateway extensions, automating notification pipelines via WhatsApp APIs, and connecting secure webhook receivers.
Optimizing Google Core Web Vitals, configuring Static Site Generation (SSG) for SEO crawlability, and migrating slow systems to cached cloud servers.
Safe software delivery relies on a structured version control workflow. I implement standard GitFlow branching models, configuring strict peer review policies and branch protection rules. Development branches require automated GitHub Actions CI checks to pass before merging. These pipelines run automated test suites, execute code linters, and audit security vulnerabilities.
To maintain high speed, the CI/CD pipeline is optimized to run automated test steps in **under 5 minutes**. Frontend pull requests generate isolated preview URLs dynamically, allowing stakeholders to review UI changes before merging to the main branch.
When delivering freelance projects, I ensure the codebase is structured for long-term maintainability. Deliverables include:
Optimizing site performance is a key part of my consulting services. I optimize frontends to achieve a **Largest Contentful Paint (LCP) < 2.0s** by using Static Site Generation (SSG), compressing assets, and prefetching bundle files. In addition, I optimize database queries and configure Redis caching layers to maintain a **sub-80ms API response via Redis**, ensuring fast, reliable service under heavy user traffic.
Verifiable custom gateway callback validation in PHP
Sanitized WooCommerce custom payment gateway callback class designed for Razorpay/PayU payment flows.
Blocks double-spending and order parameter manipulation by calculating SHA-512 checks using secure salt variables.
Payment Signature Verification Flow
// class-wc-custom-gateway.php - WooCommerce gateway callback processor
class WC_Custom_Gateway extends WC_Payment_Gateway {
public function check_callback_validity($post_data) {
$hash_string = $this->merchant_salt . '|' . $post_data['status'] . '|' . $post_data['txnid'];
$computed_hash = hash('sha512', $hash_string);
if (hash_equals($post_data['hash'], $computed_hash)) {
$order = wc_get_order($post_data['txnid']);
if ($post_data['status'] === 'success') {
$order->payment_complete($post_data['mihpayid']);
return true;
}
}
return false;
}
}Recruiter 30-Second Summary
Engineered and maintained a custom payment gateway plugin connecting e-commerce platforms with payment processors (such as PayU India). The backend manages transactions securely, verifying webhook validation states and logging transaction status dynamically.
View Payment Plugin BoilerplateProjects are accepted on either a fixed-scope basis or monthly retainer/contract format. In all engagements, clear milestones, deliverables, and communication protocols are established to ensure full delivery transparency.
Yes. I collaborate regularly with designers, product managers, and other developers using tools like Slack, Git/GitHub, Jira, and Figma to implement clean frontends and robust backends synchronously.
Repository access is managed strictly through secure, limited-permission team accounts on GitHub or GitLab. Server configuration and adjustments are executed via SSH key validation, and database credentials are kept isolated using secure environment variables.
The new cloud server environment is first built, configured with database schemas, and tested on a staging subdomain. Database writes on the old server are paused momentarily, DNS A-records are updated with a low TTL, and traffic is cut over to ensure zero lost transactions.
Yes. The WooCommerce Payment Gateway Boilerplate, WhatsApp API WooCommerce Integration, Web Scrape Data Tool, and PixGrow Image Optimizer are all published, open-source projects with public code on GitHub. They are personal portfolio projects rather than freelance client deliverables, and they demonstrate the same engineering standards applied to contract work.