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Marios PavlidisPrincipal DBA

Expertise

Capabilities by platform and discipline. Each area reflects production operational experience, not theoretical familiarity.

Oracle

  • Oracle Database administration across 12c, 18c, 19c, 21c and 23ai for business-critical single-instance, RAC and multitenant environments
  • Real Application Clusters (RAC) and Grid Infrastructure — installation, ASM, Clusterware administration, node lifecycle, rolling patching, failover analysis and capacity management
  • Data Guard and disaster recovery — physical and logical standby, Active Data Guard, Far Sync, Data Guard Broker, switchover/failover procedures and DR validation
  • Oracle Multitenant — CDB/PDB administration, cloning, refreshable PDBs, plug/unplug operations, tenant provisioning and consolidation
  • RMAN backup and recovery — backup architecture, Recovery Catalog, media management, restore validation, point-in-time recovery and recovery runbooks
  • Performance engineering — AWR/ASH analysis, execution-plan diagnosis, SQL profiles, SQL patches, SQL Plan Management, statistics management and wait-event analysis
  • Upgrades and migrations — Oracle version upgrades, Data Pump, RMAN duplicate, transportable tablespaces, cross-platform migration and low-downtime cutover planning
  • Oracle Cloud Infrastructure — Exadata Cloud Service, Base Database Service, Autonomous Database, backup/DR architecture and database-service operations
  • Oracle GoldenGate — replication architecture, integrated capture and apply, initial loads, DDL replication, monitoring, reconciliation and operational support
  • Database security — TDE, wallet and keystore administration, Unified Auditing, privilege governance, data masking and security hardening
  • Patching and lifecycle management — OPatch, Release Updates, rolling RAC patching, patch validation, rollback planning and production change control
  • Oracle APEX — workspace administration, application lifecycle management, deployment governance, authentication and production support

SQL Server

  • SQL Server 2012–2022 administration across mission-critical, high-availability, and regulated environments
  • Always On Availability Groups — architecture design, synchronous and asynchronous replication, failover strategy, listener and DNS configuration, quorum planning, monitoring, and incident resolution
  • Failover Cluster Instances (FCI) — Windows Server Failover Clustering design, shared-storage dependencies, patching, failover testing, and operational support
  • Performance engineering — execution-plan analysis, Query Store, wait statistics, blocking and deadlock analysis, index design, statistics maintenance, and capacity optimisation
  • Azure SQL Database — provisioning, migration, elastic pools, geo-replication, performance management, security configuration, and operational governance
  • SQL Server on Azure VMs — infrastructure sizing, storage and I/O configuration, high availability, backup architecture, licensing considerations, and cost optimisation
  • Backup, recovery, and DR — full, differential, and transaction-log backup strategies; log shipping; point-in-time recovery; restore validation; recovery runbooks and DR testing
  • Security and compliance — Transparent Data Encryption, Always Encrypted, Row-Level Security, SQL Server Audit, least-privilege access models, authentication hardening, and encryption governance

PostgreSQL

  • PostgreSQL 13–18 administration across on-premises, cloud, high-availability, and data-intensive environments
  • Streaming replication — primary/standby architecture, synchronous and asynchronous replication, switchover, promotion, failover procedures, replication lag analysis, and recovery validation
  • Logical replication — publication/subscription design, selective table replication, schema-change considerations, conflict handling, migration support, and operational monitoring
  • Performance engineering — EXPLAIN and EXPLAIN ANALYZE, query-plan diagnosis, index strategy, statistics maintenance, autovacuum tuning, vacuum workload management, connection pooling, and capacity optimisation
  • Monitoring and observability — pg_stat_* analysis, pg_stat_statements, snapshot-based delta monitoring, lock and blocking diagnostics, WAL/checkpoint analysis, alert thresholds, and historical workload reporting
  • Backup, recovery, and DR — pg_basebackup, pgBackRest, WAL archiving, point-in-time recovery, restore testing, recovery runbooks, and backup validation
  • Advanced indexing and AI workloads — pgvector, HNSW and IVFFlat indexes, vector distance operators, recall/performance trade-offs, index sizing, and operational tuning for similarity search
  • Extensions and ecosystem — pg_partman for partition lifecycle management, TimescaleDB fundamentals, PostGIS fundamentals, extension lifecycle management, and upgrade compatibility assessment
  • Data lifecycle and scalability — table partitioning, retention management, bulk-load optimisation, large-table maintenance, and storage growth planning
  • Security and operational governance — role design, least-privilege access, TLS, authentication configuration, auditing considerations, patching, version upgrades, and standards-based operational procedures

MongoDB

  • MongoDB 5.x–8.x administration across on-premises, cloud, and hybrid environments
  • Replica sets — architecture design, election configuration, priority and vote management, hidden and delayed members, cross-site topologies, read preference strategy, and failover testing
  • Multi-site and geo-distributed deployments — replica set member placement across data centres, arbiter strategy, write concern and read concern trade-offs, network partition handling, and site-aware cluster design
  • Sharding — shard key selection and impact analysis, hashed and ranged sharding, zone sharding for data locality, chunk management, balancer configuration, and resharding considerations
  • Performance engineering — index design, compound and partial indexes, explain output analysis, aggregation pipeline optimisation, query targeting, collection scan elimination, working set sizing, and oplog sizing
  • Monitoring and observability — mongostat, mongotop, currentOp analysis, slow query log review, Atlas Performance Advisor, replication lag monitoring, and connection pool diagnostics
  • Backup, recovery, and DR — mongodump/mongorestore, Atlas Online Archive, oplog-based point-in-time recovery, backup validation, and recovery runbook design
  • Operational lifecycle — version upgrades, FCV management, rolling maintenance, capacity planning, storage engine considerations, and change-control procedures
  • Security — role-based access control, authentication mechanisms, TLS configuration, field-level encryption, auditing, and least-privilege access design

Cloud Platforms

  • Oracle Cloud Infrastructure (OCI) — Exadata Cloud Service, Base Database Service, Autonomous Database, VM DB Systems, compute, block storage, networking, and backup/DR architecture
  • Microsoft Azure — Azure SQL Database, SQL Server on Azure VMs, Azure Database for PostgreSQL, Azure Monitor, Log Analytics, Backup vault, and networking for database workloads
  • Database cloud migration — assessment, lift-and-shift, platform-native migration (on-premises to Azure SQL, OCI, RDS), cut-over planning, rollback strategy, and post-migration validation
  • High availability and DR in cloud — Always On AGs on Azure VMs, Azure SQL geo-replication, OCI Data Guard, cross-region standby design, and RPO/RTO alignment with cloud networking constraints
  • Storage and I/O configuration — Premium SSD and Ultra Disk sizing for SQL Server on Azure VMs, OCI block volume performance tiers, IOPS/throughput planning, and tempdb and data file layout
  • Cloud cost and licensing — Azure Hybrid Benefit, SQL Server licensing on VMs, reserved capacity, elastic pool right-sizing, OCI BYOL, and cost governance across database services
  • Observability in cloud — Azure Monitor metrics and alerts, Log Analytics queries, OCI Monitoring and Logging, slow query diagnostics, and performance baseline management
  • Infrastructure-as-code — ARM templates and Bicep for Azure database resources, OCI Resource Manager (Terraform), repeatable environment provisioning, and configuration governance

High Availability & Disaster Recovery

  • HA/DR architecture design across Oracle (RAC, Data Guard, Far Sync), SQL Server (Always On AG, FCI, Log Shipping), PostgreSQL (streaming replication, Patroni), and MongoDB (replica sets)
  • RPO and RTO analysis — target definition, gap assessment against existing architecture, trade-off documentation, and stakeholder alignment
  • Synchronous and asynchronous replication trade-offs — data loss exposure, performance impact, network latency constraints, and appropriate use per workload tier
  • Failover and switchover procedures — planned and unplanned scenarios, step-by-step runbook development, pre- and post-failover validation checklists
  • Failover testing — scheduled DR drills, test-environment simulation, real failover execution in maintenance windows, and outcome documentation
  • Cross-platform DR strategy — heterogeneous database estates, mixed on-premises and cloud topologies, single-pane monitoring, and unified recovery governance
  • HA/DR for regulated environments — compliance alignment, audit evidence for DR testing, recovery SLA documentation, and change-control integration
  • Incident response — structured escalation, triage under pressure, root-cause analysis, and post-incident review with corrective actions

Performance Engineering

  • Workload characterisation — baseline capture, peak vs steady-state profiling, resource consumption analysis, and bottleneck identification across CPU, memory, I/O, and network
  • Execution plan analysis — Oracle AWR/ASH and SQL Monitor, SQL Server Query Store and execution plans, PostgreSQL EXPLAIN ANALYZE — plan regression detection and stabilisation
  • Wait event and contention analysis — wait statistics, blocking chains, deadlock graph analysis, latch contention, and lock escalation diagnosis across platforms
  • Index strategy — index design, redundant index identification, missing index assessment, maintenance windows, statistics management, and fragmentation remediation
  • Query and SQL tuning — rewrite guidance, join strategy, predicate push-down, parameterisation, plan forcing, and developer collaboration on high-impact workloads
  • Capacity planning — historical trend analysis, growth modelling, resource headroom assessment, storage projection, and hardware or cloud tier sizing recommendations
  • Performance benchmarking — workload replay, pre/post change comparison, regression testing after upgrades or schema changes, and evidence-based sign-off
  • Automation and monitoring — proactive slow-query alerting, scheduled plan capture, long-running job detection, and performance dashboards for operational visibility

Database Security

  • Access control and privilege governance — role design, least-privilege implementation, privilege review and remediation, separation of duties, and user lifecycle management
  • Encryption at rest — Transparent Data Encryption (SQL Server, Oracle TDE), PostgreSQL pgcrypto, OCI and Azure key management, wallet and keystore administration
  • Encryption in transit — TLS configuration for Oracle, SQL Server, PostgreSQL, and MongoDB; certificate management; and client connectivity validation
  • Advanced encryption — Always Encrypted (SQL Server), Oracle Advanced Security, MongoDB field-level encryption, and application-tier key management patterns
  • Auditing and logging — SQL Server Audit, Oracle Unified Auditing, PostgreSQL pgaudit, MongoDB audit log — scope definition, log management, and SIEM integration
  • Authentication hardening — password policy, Kerberos and AD integration, certificate-based auth, Windows Authentication, and eliminating shared or default accounts
  • Row- and object-level security — Row-Level Security (SQL Server), Oracle VPD, PostgreSQL RLS — design, implementation, and testing
  • Compliance-aligned hardening — CIS benchmark application, vulnerability assessment, remediation planning, and evidence preparation for security and compliance reviews

Migration & Modernisation

  • Migration assessment — source inventory, schema complexity analysis, incompatibility identification, dependency mapping, and effort estimation
  • Cross-platform migration — Oracle to PostgreSQL, SQL Server to Azure SQL, on-premises to cloud — schema conversion, data type mapping, and stored procedure remediation
  • Migration tooling — AWS Schema Conversion Tool, pgloader, ora2pg, SQL Server Migration Assistant (SSMA), Data Pump, RMAN Duplicate, and custom ETL pipelines
  • Low-downtime cut-over strategies — change data capture, dual-write patterns, replication-assisted cut-over, and rollback validation before and after switch
  • Cut-over planning — detailed runbook authoring, go/no-go criteria, stakeholder communication plan, maintenance window coordination, and contingency procedures
  • Post-migration validation — row count reconciliation, data integrity checks, query equivalence testing, performance baseline comparison, and application smoke testing
  • Modernisation patterns — legacy monolith decomposition, schema normalisation, NoSQL evaluation, cloud-native database service adoption, and phased migration planning
  • Operational handover — target environment documentation, team enablement, monitoring handover, and post-migration support period governance

DBA Operations & Leadership

  • DBA team structure and development — multi-level team design, career pathway definition, skills gap assessment, mentoring, and knowledge transfer programmes
  • Operational standards — naming conventions, documentation frameworks, runbook governance, change-control integration, and peer review processes
  • Incident and problem management — structured triage, escalation paths, on-call coordination, root-cause analysis, post-incident review, and corrective action tracking
  • Monitoring framework design — metric selection, threshold definition, alerting hierarchy, dashboard design, and escalation integration with ITSM tooling
  • Automation — scripted health checks, routine maintenance automation (backups, index rebuilds, statistics), environment provisioning scripts, and PowerShell/Bash tooling
  • Capacity and lifecycle management — growth forecasting, decommission planning, version end-of-life tracking, patch scheduling, and environment refresh coordination
  • Vendor and platform evaluation — proof-of-concept design, feature assessment, licensing analysis, total cost of ownership modelling, and recommendation reporting
  • Stakeholder engagement — translating database risk and capacity concerns into business-relevant language for architects, project managers, and senior leadership