Modernising Together: How Thurrock Council, Mastek and AWS Are Delivering a Complex Cloud Migration
Thurrock Council, a unitary authority serving around 176,000 residents in Essex, set out to move a large, ageing on-premises estate onto AWS without disrupting frontline services. Thurrock selected Mastek as its delivery partner, working closely with AWS's account and solutions architecture teams throughout.
The estate proved more complex than initial assessment suggested, and Thurrock, Mastek and AWS worked through that complexity together: deeper discovery, detailed technical design, and a wave-based migration now underway across around 220 servers. The programme is backed by AWS's Migration Acceleration Program (MAP), and the AWS environment is already live with real production usage ahead of full migration completion.
Industry
Geography
UK
Service Line
Digital Engineering & Experience; Cloud Migration; Cloud Engineering
Technology Stack
AWS Landing Zone, AWS MGN, AWS Workspaces, AWS Backup/S3
About Thurrock Council
Key activities of the Council span the gamut of planning and growth, business development, education, environment and safety, travel and transport, health, community and living, waste management, and leisure and culture.
Challenge
Thurrock's on-premises servers and Citrix VDI platform were approaching end-of-support. The estate supports services that cannot simply stop for a migration weekend, including social care case management, revenues and benefits, land charges and registry services, and library systems.
The Council's own RVTools export gave a useful starting inventory, but not enough detail to migrate safely. Together, Thurrock and Mastek carried out significantly deeper discovery and dependency analysis, mapping several hundred thousand recorded network connections across the estate. Several critical areas, including identity and Entra integration, security tooling, operations and backup and network architecture, had only minimal documentation or none at all, and had to be built from scratch alongside the technical debt this uncovered.
Solution
Migration is being delivered in planned waves agreed jointly by Thurrock and Mastek, beginning with an 8-server pilot that validated the approach ahead of subsequent migration waves. Most servers are being rehosted with minimal downtime; where ageing software or technical debt made that the wrong choice, Thurrock and Mastek instead used a “build-ahead” approach, standing up clean, current-generation servers that Thurrock’s own teams configure and validate.
Rather than redesign Thurrock’s identity environment, Mastek extended it into AWS, and closed gaps in existing documentation to produce the detailed technical designs a supportable environment needed.
The migration is also being used to optimise, not just relocate: a consolidated SQL Server hosting model makes full use of Thurrock’s existing Microsoft licensing, and end users are moving from Citrix to Amazon WorkSpaces as a genuine modernisation. AWS’s AI-enabled tooling supported discovery and network analysis throughout, and the programme draws on AWS MAP and the UK public sector’s OGVA pricing to strengthen the business case.
Impact
Already achieved:
- AWS Landing Zone independently tested against the AWS Well-Architected Framework, CIS AWS Foundations Benchmark and AWS Foundational Security Best Practices: 100% pass rate before any production migration.
- An 8-server pilot migration wave successfully executed, validating the approach ahead of subsequent migration waves.
- Nine detailed technical designs now in place across identity, networking, backup, operations and the target AWS architecture, several for the first time.
- The AWS environment already live and in production use, with billed consumption already clearing AWS’s $100,000 annual usage bar for production-grade partner solutions.
Projected, once migration completes (targeted around January 2027):
- Up to a 43% reduction in modelled infrastructure run cost; a business-case model, not yet a realised saving, dependent on completed migration scope and actual consumption.
- Retirement of legacy Citrix/Ivanti VDI infrastructure and licensing, as the transition to Amazon WorkSpaces completes.
- Continued AWS MAP funding support through to migration completion, as qualifying scope is evidenced to AWS.
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Why It Matters
Thurrock’s programme shows what a council’s institutional knowledge, a delivery partner’s migration expertise and AWS’s platform and programme support can achieve together: understanding a more complex estate than expected, extending identity safely, and choosing the right migration pattern for each workload. Thurrock, Mastek and AWS built this programme as one team.