Sr DataBase Architect (ES) - SQL Server, Aurora PostgreSQL y Babelfish

DESCRIPTION We're looking for a senior Database Architect to improve the database of a legacy ERP and assess a possible migration from SQL Server to Amazon Aurora PostgreSQL with Babelfish. IMPORTANT BEFORE APPLYING • FULL AUTONOMY: you'll be the top authority on the database. The team will work alongside you, but no one else will set the diagnosis, priorities, or decisions. • LEGACY EXPERIENCE: you must have modernized databases for legacy applications in production without stopping the business. • HANDS-ON WORK: beyond recommending, you'll write SQL and scripts, build PoCs, and implement improvements. • SQL SERVER AND POSTGRESQL: you need advanced SQL Server experience, solid PostgreSQL experience, and the ability to work across both. • INDEPENDENT JUDGMENT: the migration isn't a done deal. You need to be able to recommend a go/no-go and make the case for SQL Server if that's the better call. • LOCATION: based in Europe, with hours overlapping Spain (CET/CEST). • LANGUAGE: professional-level Spanish or higher. • LONG-TERM POTENTIAL: genuine possibility of long-term work if it's a good fit. THE CONTEXT We're a European software company with an ERP made up of around forty modules covering payroll, scheduling, time tracking, invoicing, and accounting. It's a database-heavy system with critical processes and legal implications. Two platforms currently run side by side in production: • LEGACY LAYER: a proprietary 4GL platform, written in FDL and rendered through WinForms on .NET Framework 3.5. It runs on an in-house transaction DSL and remains the source of truth. • MODERN LAYER: a .NET 10, Blazor Server, and SQL Server application. Most of its code is generated every night from the legacy system through a transpiler. SQL Server sits at the core of the system and has built up technical debt in schema design, indexing, query parameterization, transactions, concurrency, timeouts, and observability. THE POSSIBLE MIGRATION We're exploring Amazon Aurora PostgreSQL with Babelfish, but the decision hasn't been made. Babelfish lets Aurora PostgreSQL accept SQL Server connections and run most T-SQL over TDS. It can cut down on the changes a migration would require, but it doesn't offer full compatibility. We need to validate it against our real workload. RESPONSIBILITIES • Build a baseline and review schemas, dependencies, models, indexes, statistics, queries, transactions, workloads, and critical flows. • Spot and prioritize performance issues, blocking, deadlocks, concurrency, plan cache, timeouts, and resource consumption. • Implement observability with per-query diagnostics, trends, and actionable alerts. • Review how the legacy system, the transpiler, and the generated code build and run queries, and apply durable fixes at the right source. • Assess Babelfish compatibility: T-SQL, data types, collations, functions, procedures, triggers, permissions, transactions, and cross-database dependencies. • Build a proof of concept and compare both engines against the same inputs, validating results, integrity, concurrency, and performance. • Evaluate high availability, recovery, security, scaling, costs, and operational constraints. • Deliver a go/no-go recommendation and, if warranted, define migration, reconciliation, cutover, and rollback. • Implement the first improvements and transfer knowledge to the internal team. EXPECTED INITIAL OUTCOMES • Technical assessment grounded in evidence from the real system. • Prioritized backlog with the first optimizations verified on SQL Server. • Performance and observability baseline. • Compatibility matrix and proof of concept with Babelfish. • Go/no-go recommendation and roadmap for the chosen path. MUST-HAVE • Strong command of query tuning, execution plans, indexing, statistics, transactions, locking, concurrency, and performance diagnostics. • Experience with assessments, migrations, validation, reconciliation, cutover, and rollback. NICE TO HAVE • Experience with Aurora PostgreSQL, Babelfish, Babelfish Compass, or AWS Database Migration Service. • Familiarity with .NET, Blazor Server, and data access patterns from web applications. • Experience with ERPs, critical systems, 4GL platforms, in-house DSLs, or generated codebases. TO SUBMIT YOUR PROPOSAL • Describe a similar case involving SQL Server and a legacy application: starting point, the work you personally did, and the results. • Share your experience with PostgreSQL, Amazon Aurora, or Babelfish. If you haven't used Babelfish, describe the closest migration you've done. • Summarize how you'd approach the assessment and what criteria you'd use to decide whether we should migrate. • Share your availability, time zone, and usual rate.