Cloud and platform
Migrating a monolith to the cloud
A phased move of a monolithic application with assessment, pilot, parallel running and a rollback plan.
Fictional scenario. An example situation that illustrates the approach. It is not a client project and describes no measured results.
Business problem
A fictional B2B application runs in an ageing data centre. Updates are risky and the hosting contract is ending.
Assumptions
- A landing zone exists or will be built.
- The database can be replicated.
- There is a maintenance window.
Constraints
- No data loss.
- A rollback plan for every step.
- Minimal disruption for customers.
Reference architecture
Components by stage — an illustration, not a running system and not a certified design.
01Assessment
- Inventory
- Dependencies
- Costs
02Preparation
- Landing zone
- Network link
03Migration
- Database replication
- Parallel running
- Cut-over
04After migration
- Monitoring
- Cost optimisation
The diagram as a list
| Stage | Components |
|---|---|
| Assessment | Inventory, Dependencies, Costs |
| Preparation | Landing zone, Network link |
| Migration | Database replication, Parallel running, Cut-over |
| After migration | Monitoring, Cost optimisation |
Interfaces
| From | To | Via |
|---|---|---|
| Data centre | Cloud | VPN or private link |
| Old database | New database | Replication |
| DNS | New environment | Gradual switch |
Data flow
- Data is replicated continuously.
- The new environment is tested in parallel.
- Traffic is switched gradually.
- The old environment stays ready for rollback.
- It is turned off once stable.
Security boundaries
- Encryption in transit.
- Permissions reviewed in the new environment.
- Secrets moved to a store.
Where a person approves
- Every traffic switch.
- Turning off the old environment.
Delivery phases
01 · Assessment
Inventory, risks, plan.
02 · Pilot
A non-production environment.
03 · Cut-over
Production with a rollback plan.
04 · Optimisation
Right-sizing and costs.
Limitations
- The monolith stays a monolith — modernisation is a separate step.
- Licences may limit the options.
Trade-offs
- Lift and shift — fast but without cloud benefits.
- Parallel running — costlier for a while but safer.
Related services
Related assessments
Integration patterns used
Facing something similar?
We start with an assessment of where you are and propose a realistic first phase.