Mike Hall
Principal Software Engineer / Systems Architect
- Location Chicago, IL
- Email mike@just3ws.com
- Phone (847) 877-3825
- Web just3ws.com
- LinkedIn linkedin.com/in/just3ws/
- GitHub github.com/just3ws
Professional Summary
Principal Software Engineer specializing in high-consequence legacy modernization, distributed systems architecture, and platform resilience. Combines 20+ years across software engineering and platform architecture with OpenTelemetry distributed tracing, cross-lane boundary mediation, and zero-downtime data migrations across Ruby on Rails, PostgreSQL, and cloud infrastructure.
Target focus
- Platform Architecture & Legacy Modernization
- Cross-Domain Boundary Architecture & Governance
- OpenTelemetry & Distributed Trace Context Propagation
- High-Consequence Incident Escalation & Root Cause Analysis
- Zero-Downtime Data Migrations & Schema Partitioning
Experience & Leadership
Associate Director, Staff Engineer
Target Focus: Progressed from Digital Origination Team Lead to Software Architect for the Acquisition Lane, converting to Associate Director, Staff Engineer upon corporate architecture track restructuring, while founding the ACQ Enablement team and leading the OpenTelemetry Working Group to establish the Enterprise Trace across high-volume customer acquisition flows (Rails, MuleSoft, Mainframe).
- Technical Leadership & Team Consolidation: Progressed from Digital Origination Team Lead to Software Architect for the Acquisition Lane, merging two attrition-impacted teams into a unified, high-functioning engineering unit before converting to Associate Director, Staff Engineer upon corporate architecture track restructuring.
- ACQ Enablement Founding & Engineering Mandates: Founded and technically led the ACQ Enablement team to protect core engineering concerns from product feature pressure: driving platform stabilization, legacy modernization, system process mapping, architecture documentation, PII remediation, and fraud investigations.
- Observability & Enterprise Trace: Founded and led the OpenTelemetry Working Group (OTel WG) to establish the Enterprise Trace across high-volume customer acquisition flows, connecting a complex Rails distributed monolith, MuleSoft, and IBM mainframe backends to eliminate blind spots and align engineering around real-time service maps.
- AI-Augmented Systems Investigation: Introduced privacy-conscious local AI workflows for legacy code analysis and engineering support, expanding investigative capacity while keeping human review, security constraints, and source evidence explicit.
Development Manager — Founder Transition & Acquisition Handoff
Target Focus: Conducted rapid architecture discovery, compliance verification, and operational risk assessment for a multi-tenant healthcare SaaS platform serving 130+ clinics through a founder transition and acquisition handoff.
- Architecture Discovery & Operational Risk Assessment: Built a rapid 90-day system inventory and risk model spanning application codepaths, infrastructure dependencies, access boundaries, and operational risks.
- Production & Compliance Governance: Established release verification gates across the deployment pipeline of a platform servicing 130+ clinics, blocking unvalidated changes prior to HIPAA compliance review and business sign-off.
Senior Backend Developer
Target Focus: Modernized search and asynchronous messaging pipelines under live production load, executing zero-downtime Rails framework upgrades and database relational indexing.
- Search Infrastructure Simplification: Replaced legacy external search clusters (Sphinx) with native MySQL full-text search and optimized relational indices, eliminating external service dependencies and reducing platform infrastructure footprint.
- Zero-Downtime Platform Upgrades: Led Ruby and Rails framework upgrades across multiple core applications, sequencing database migrations and dependency updates to maintain uptime during platform modernization.
Senior Software Developer
Target Focus: Architected the multi-database PostgreSQL and MySQL partition split, decoupling monolithic campaign dispatch queues with dual-write synchronization shims.
- Legacy Boundary Isolation: Decoupled critical legacy constraints behind explicit service boundaries, eliminating high-risk direct database dependencies and establishing clean execution paths.
- Data Access & Query Optimization: Replaced ad-hoc global state access with structured query patterns and multi-tier caching strategies, accelerating throughput for high-volume database reads.
- Frontend Test Hardening: Hardened the Ember.js frontend test suite across complex CRM user workflows, enforcing testable state boundaries and reducing regressions in customer-facing flows.
- Test-Driven Observability: Established test-driven observability patterns across legacy PHP codepaths, shortening developer feedback loops during high-risk production debugging.
Engineering Learning & Development Business Partner
Target Focus: Designed analytical fraud detection queries in Vertica, spiked anomaly detection in Clojure/Hadoop, and implemented a centralized merchant taxonomy service in Java and MySQL.
- Built merchant analytics tools in Ruby and CouchDB, surfacing market insights for global sales operations.
- Designed analytical fraud detection queries in Vertica and conducted exploratory spikes on Hadoop and Clojure-based anomaly detection tools.
- Implemented a centralized merchant taxonomy service in Java (ActiveWeb/ActiveJDBC) and MySQL, eliminating categorization drift across distributed product teams.
- Redesigned the global engineering onboarding curriculum, standardizing technical practices and shortening time-to-first-commit for new hires.
Selected Production Projects
Creator
Rails 8 platform for multi-source job ingestion, semantic matching, and application automation, built as a working laboratory for local-first LLM orchestration and treating scraped third-party text as hostile input.
- Data Ingestion & Normalization: Built a multi-source Rails ingestion pipeline and PostgreSQL storage schema, unifying fragmented job market datasets for structured downstream analysis.
- Semantic Search & Matching: Implemented vector search embeddings via pgvector, enabling high-precision semantic matching between complex candidate profiles and job requirements.
- Local-First AI Orchestration: Designed a provider-agnostic LLM orchestration layer behind a YAML-driven model registry, local-first by default (llama.cpp/Ollama primary, hosted Claude as fallback), so routine inference never leaves the machine while a stronger hosted model can be selected per call site.
- Prompt Injection Defense: Built a four-stage guardrails pipeline (normalize, weighted heuristic scan, risk classify, output validate) screening every untrusted scraped document before it reaches a model, scoring known injection patterns plus an instruction-density heuristic to secure ingestion against hostile inputs.
- Browser Extension & Lifecycle Capture: Built an MV3 Chrome extension with 16 provider adapters that extracts postings from live ATS pages and captures the full application lifecycle (questions asked and answers given) back into the platform.
- Static Signal Integration: Injected static analysis rules and architectural constraints into model context windows, preventing drift between generated outputs and system security contracts.
Creator & Forensic Engineer
Recorded, and later restored, an archive of 214 technical interviews with practitioners from the Ruby, JVM, and Software Craftsmanship movements, using a local-only AI pipeline to transcribe, structure, and cross-link two decades of primary-source material into a searchable knowledge graph.
- Local-Only AI Restoration Pipeline: Built a Whisper and local-LLM pipeline that transcribes, diarizes, and structures long-form interview audio entirely on-device, keeping a large private media corpus off third-party inference services.
- Schema-Validated Content Platform: Runs on a contract-validated data layer: every interview, asset, and transcript is checked against an explicit schema at build time, with referential-integrity checks that fail the build rather than publishing broken data.
- Semantic Cross-Linking & Taxonomy Generation: Generates a topic taxonomy, knowledge graph, and semantic cross-links across the corpus, turning an unstructured media archive into navigable, individually indexed pages.
- Primary-Source Capture: Conducted the original interviews on-site at GOTO Conference, Software Craftsmanship North America, RailsConf, and WindyCityRails, with practitioners including Dave Thomas, Stuart Halloway, Corey Haines, Sandro Mancuso, and Micah Martin.
- Digital Archaeology: Recovered and reconstructed material from defunct platforms and web archives, reconciling incomplete metadata across sources to restore provenance for recordings that would otherwise have been lost.
Creator
Built and operate three MCP (Model Context Protocol) servers that expose live system state as callable tools to any MCP client, alongside the Claude Code skills, context-isolated subagents, and commit-time checks that keep agent work bounded and reviewable.
- Bidirectional Knowledge Server: Built ctx-mcp, an MCP server fronting a PostgreSQL knowledge suite that agents both query and write back to, so methodologies and lessons learned in one session are retrievable in the next rather than re-derived.
- Telemetry-Driven Diagnosis: Built o2-mcp, exposing on-demand OpenObserve telemetry (errors, slow spans, failed jobs, distributed traces) as agent-callable tools, so an agent diagnoses a running system from observed behavior instead of inferring from source.
- Context as a Budgeted Resource: Designed context-isolated subagents that keep high-volume audit work out of the main conversation's context window, with per-client registration tooling and pre-commit hooks that reject any agent asset that isn't self-describing.
Core Skills & Competencies
01
- Platform Architecture & Legacy Modernization
02
- Cross-Domain Boundary Architecture & Governance
03
- OpenTelemetry & Distributed Trace Context Propagation
04
- High-Consequence Incident Escalation & Root Cause Analysis
05
- Zero-Downtime Data Migrations & Schema Partitioning
06
- Ruby on Rails, PostgreSQL, Sidekiq & Redis
07
- AWS, Docker, Kubernetes & CI/CD Pipelines
08
- Privacy-Conscious Local AI Orchestration & Tooling
Additional Experience
- Senior Software Developer, BenchPrep : Owned enterprise assessment workflows, leading correctness and platform security in a high-concurrency environment.
- Senior Software Developer, ReachLocal : Owned API design and modernization strategy, leading incremental legacy migration for a high-volume digital marketing platform.
- Open-Source Transition Lead, Coderwall : Hired as a contractor by the founder to lead the open-source transition of the Coderwall developer reputation platform, a Y Combinator-backed professional network for software engineers (856 GitHub stars, 304 forks). Delivered security hardening, proprietary service extraction, infrastructure modernization, and community leadership as the top contributor to the open-source codebase.
- Principal Consultant, Tandem : Owned strategic technical assessment and on-site operational evaluation, leading architectural realignment and scope correction for a high-risk federal software program (DoD MEPS). Brought in to an over-committed engagement following an engineering-team departure.
Career Foundations
Built and operated enterprise integrations, transactional systems, and early web products across consulting and product organizations, establishing the production discipline and community-centered craftsmanship that still shape my leadership.
- Revenue-critical commerce: Designed real-time inventory, locking, and fulfillment services for a high-volume ticket marketplace later acquired by a major industry operator.
- Consulting and software craftsmanship: Delivered systems across client environments while mentoring engineers, adopting Ruby and Rails, and helping build Chicago's craftsmanship community.
- Enterprise and operational systems: Built integration and operational software across large organizations, grounded in .NET, SQL, messaging, production support, and direct user needs.