Modernizing the core without shutting down the bank: the wrap-and-migrate model

Why big-bang migrations fail

In a big-bang migration, the institution spends months or years preparing a new system and, over one weekend, switches off the old one and turns on the new one with all customers, accounts and products. If everything goes well, the change is fast. If something fails, the impact hits the entire operation at once.

The typical problems repeat themselves: data that does not migrate as expected, end-of-day processes that behave differently, integrations no one documented and teams that must learn everything at once. In addition, while the project lasts, the institution usually freezes changes to the old core and stops launching products.

The wrap-and-migrate model reduces that risk by dividing it. Instead of one big leap, it proposes a sequence of small steps, each with its own value and with the option to roll back.

The model in four steps

1. Wrap the current core with an integration layer that exposes its functions as modern APIs.
2. Launch new channels in parallel, connected to the current core through that layer.
3. Activate cross-cutting compliance and fraud prevention that watch every layer.
4. Migrate by module, moving products and accounts to the new core one at a time, at the pace the institution decides.

The home page shows this journey as an animation and the platform map places each module. Each step is detailed below.

Step 1: wrap the current core

AloConnect is installed alongside the existing system and translates its protocols (ISO 8583, SOAP, flat files) into REST APIs and ISO 20022 messages. Nothing is switched off: the core remains the source of truth, but it can now talk to new channels and partners without point-to-point integrations.

This step has value on its own. It provides visibility into the health of integrations (latency, errors, volume), centralizes access security and lets you connect fintechs, wallets or correspondents in a single language. It is also the moment to document what the core actually does, which is essential for migrating later.

What to define in this phase

• Which core functions are exposed first (balance inquiries, transactions, transfers).
• Which access controls and audit logs apply to each API.
• How latency and errors are monitored, and who responds to alerts.

Step 2: launch channels in parallel

With the core wrapped, the institution can launch digital products without waiting for the migration: a digital wallet, payment acceptance on phones with Punto Digital, a business portal or video banking service. All of them run on the current core through the integration layer.

This changes the internal conversation. The modernization project stops being a cost with a distant date and starts producing visible results within months. Customers notice the improvement and the team gains experience with the new platform before touching the accounting core.

Step 3: cross-cutting compliance and fraud prevention

New channels bring new risks. That is why, in parallel, AloCompliance is activated for identity verification (KYC and KYB) and transaction monitoring, and AntiFraude to detect anomalous behavior. Sitting on top of the integration layer, they see operations from every channel and from both cores, old and new.

Having a single risk view during the transition is key: it prevents control gaps while some products live in one system and others in the other, and it produces the evidence the supervisor asks for.

Step 4: migrate by module

When it makes business sense, products move to AloCore one by one. There is no single cutover date: each migration is a bounded project, with its own test plan, window and rollback plan.

A typical order

1. New products that are born directly in the new core and require no data migration.
2. Simple deposit products, such as savings accounts with straightforward rules.
3. Loan portfolio, with its schedules, interest and collateral, configured with PIE.
4. Complex products or those with long histories, once the team has mastered the process.

Accounting coexistence

While two cores coexist, each product has a single source of truth, defined in writing. Accounting is consolidated from both systems, and daily reconciliation compares balances and transactions to detect differences the same day. AloCore's real-time ledger makes that control easier.

Data: the heart of every migration

Every product that moves to the new core brings its data: customers, balances, transaction history, agreed terms and documents. The quality of that migration determines success more than any other variable. A proven method has five stages:

1. Profiling. Analyze source data to find duplicates, empty fields and inconsistent values before designing anything.
2. Mapping. Document how each field of the old system is transformed into the new one, including implicit business rules.
3. Cleansing. Fix at the source what can be fixed (addresses, IDs, statuses) and decide what to do with the rest.
4. Dress rehearsals. Run the full migration several times in a test environment, reconciling balances to the cent.
5. Business validation. Have user areas review a sample of customers and products before the real window.

Dress rehearsals are the project's best investment: each run reduces errors and the length of the migration window. When two consecutive rehearsals reconcile with no manual intervention, the product is ready to move.

Risks and how to mitigate them

Project governance

The model works when each phase has clear entry and exit criteria. Before migrating a product, define how you will measure success (balanced accounts, response times, complaints), how long both systems will run in parallel and under which conditions you roll back.

Inform the supervisor as appropriate. Relevant changes to critical systems and the outsourcing of technology services have their own rules in each country; involving compliance from the first step avoids surprises.

How to get started

• Inventory the current core's integrations and who depends on each one.
• Choose a first use case with visible value: a new channel or an integration with a partner.
• Define the metrics that will show progress to management.
• Estimate the impact with the ROI calculator and compare it with the full-replacement alternative.

If your institution is still deciding on its core model, the guide In-house core banking vs. SaaS complements this reading.