Skip to content
CipherCruCipherCru

Menu

Utilities

Retiring a mainframe in slices

A billing mainframe nobody could safely change, replaced one slice at a time while it kept running.

Client
Brindley Water
Sector
Utilities
Engagement
Modernization
Duration
16 months

Why they called us

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

The problem we were handed

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

What was actually going wrong

  • Lorem ipsum dolor sit amet, consectetur adipiscing elit.
  • Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
  • Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Notes mapping an existing system, spread across a desk
Six weeks of mapping before a line of code was written.

How we worked

The sequence we followed, and why each stage had to come before the next.

Map what the system actually does

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Agree what must not break

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Move one slice, in production

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Repeat until the old system is idle

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

Turn it off, with the client's hand on the switch

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

What we built

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

  • One record of truth per domain

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

  • A translation layer, not a rewrite

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

  • Observability from day one

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

  • Rollback at every step

    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

How the Brindley Water system was structured during migration
The strangler layer that let both systems run at once.

Reading the diagram

  1. The source system, left running throughout.
  2. The translation layer that reads from it.
  3. The new service, taking one slice of traffic at a time.
  4. The shared datastore both sides write to during migration.

The system in full

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

The complete Brindley Water architecture after migration
The architecture as it stood at handover.

Reading the diagram

  1. The source system, left running throughout.
  2. The translation layer that reads from it.
  3. The new service, taking one slice of traffic at a time.
  4. The shared datastore both sides write to during migration.

What changed

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

0

Hours of downtime

Across sixteen months and eleven cutovers.

11

Slices migrated

Each one live in production before the next began.

64%

Lower running cost

Measured twelve months after the mainframe was switched off.

3

Weeks to first slice

Billing enquiries moved first, as the lowest-risk path.

Before and after

Measured on the same terms, twelve months apart.

Billing run

31 hours40 minutes

46xfaster

Change lead time

14 weeks2 days

35xfaster

Engineers who can deploy

219

9xmore

They never asked us to stop billing customers while they worked. That constraint shaped everything, and they took it seriously from the first meeting.
Portrait of Priya RamanathanPriya RamanathanDirector of Technology, Brindley Water

Other case studies

Engagements that shared a constraint, a sector, or a way of working.

Thackray Health: Making patient data available without moving it
Thackray HealthHealthcare

Making patient data available without moving it

9x

faster record retrieval

Read the case study
Corran Logistics: Replacing a build-versus-buy decision with a third option
Corran LogisticsLogistics

Replacing a build-versus-buy decision with a third option

£1.4m

saved against the buy quote

Read the case study
Ellery Wealth: An AI pilot that we recommended stopping
Ellery WealthFinancial services

An AI pilot that we recommended stopping

6

weeks to a clear answer

Read the case study

Have a problem shaped like this one?

Tell us the constraint you are working under. We will tell you how we would approach it.

Start a project

Strictly necessary cookies are always on. Every other category is off until you turn it on, and you can come back and change this at any time.

Strictly necessaryEssential for the site to function: page navigation, security, session management, and remembering the cookie choices you make here.
Always on
FunctionalRemembers choices you make, such as language, region or display preferences, so the site opens the way you left it.
Performance and analyticsPerformance and analytics cookies show us how the Website is used: which pages are visited, how long is spent on them, where visitors came from, and what errors occur. They are set by Google Analytics and by HubSpot, whose cookies also link the pages you viewed to any enquiry you later send us.
Marketing and targetingTracks browsing activity to measure advertising and show relevant ads. We set none of these today, and will not without your opt-in.