PHP Developer for Monolith Decomposition & DB Optimization

Title: Senior PHP & Backend Developer – Legacy Monolith Decomposition & Database Optimization
Project Type: Fixed Price

Budget: $8,400 USD (Strict Cap / Milestone-based)

Duration: 6 Weeks (1.5 Months)

Required Skills: PHP, Laravel, Symfony, MySQL, PostgreSQL, Redis, RESTful API, Software Architecture.

Project Overview
We are seeking an expert Senior PHP / Backend Developer to spearhead the re-engineering and performance optimization of our core e-commerce server infrastructure.

The primary objective is to systematically decouple critical domain modules from a tightly-coupled legacy monolith, optimize slow-running SQL queries, eliminate database deadlocks under peak transactional loads, and deliver a high-throughput, secure API layer for frontend integration. This is an intensive, 6-week contract requiring complete technical autonomy and immediate delivery.

2. Scope of Work
The selected engineer will take full ownership of the following technical execution streams:

Monolith Decomposition & Refactoring: Codebase dependency audit. Clean isolation of core business domains using Domain-Driven Design (DDD) principles, migrating legacy logic into decoupled, maintainable service layers without introducing production downtime.

Database Performance Tuning: Comprehensive schema and query profiling (utilizing EXPLAIN ANALYZE). Restructuring composite indexes, resolving data-lock bottlenecks, and optimizing high-frequency transactional execution paths across relational databases (MySQL/PostgreSQL).

Caching & Queue Architecture: Designing and embedding advanced caching invalidation strategies via Redis. Offloading intensive synchronous processes into robust asynchronous background jobs using message queues.

Secure API Engineering: Designing, writing, and documenting clean, versioned RESTful API endpoints. Enforcing strict validation layers, OWASP data-handling compliance, and military-grade encryption for all customer Personally Identifiable Information (PII).

3. Schedule & Milestones
Disbursements are strictly contingent upon successful integration into our staging environment and passing all automated test suites:

Milestone 1 (Weeks 1–2) — $2,800 USD: Database schema profiling, execution plan optimization, index refactoring, and resolution of transactional locking bottlenecks. Delivery of verified query-speed acceleration logs.

Milestone 2 (Weeks 3–4) — $2,800 USD: Decoupling of core domain modules into structured service containers, deployment of versioned RESTful API endpoints, and integration of the Redis caching layers.

Milestone 3 (Weeks 5–6) — $2,800 USD: Comprehensive unit/integration test coverage enforcement, integration of security controls (PII protection/OWASP parameters), stress/load testing verification, and final transfer of complete technical documentation.

4. Non-Negotiable Quality Gates
The project is only deemed complete and milestones released when the following operational standards are met:

Time & Activity Tracking: All working hours must be logged exclusively through the official Freelancer.com Desktop App. Manual time entries are strictly blocked and will not be authorized for milestone release.

Code Quality Assurance: The newly written or refactored backend logic must achieve a minimum automated test coverage floor of ≥ 85% (Unit/Integration tests).

Latency Benchmarks: Under simulated peak user loads, the optimized target API endpoints must maintain a response latency of ≤ 200ms.