Coreless Banking Goes Mainstream: TOGAF Method Meets the BIAN Map
Banks are pairing TOGAF's architecture method with BIAN's banking service landscape to decompose monolithic cores into swappable, API-first components — 'coreless banking' has moved from consortium whitepaper to mainstream modernization strategy.
What Happened
Core modernization has converged on a recognizable playbook. BIAN — the Banking Industry Architecture Network — publishes a standardized service landscape that slices banking into hundreds of well-defined service domains with semantic APIs, and its 'coreless banking' initiative demonstrates how those domains can be assembled from interchangeable, best-of-breed components. On the method side, banks keep reaching for TOGAF: its ADM cycle governs how the transformation is scoped, road-mapped, and kept honest, while BIAN supplies the banking-specific reference content TOGAF deliberately leaves open.
The migration pattern that has won is progressive rather than big-bang: cloud-native platforms and API-first vendors increasingly describe their catalogs in BIAN terms, and banks peel capabilities off the legacy core one domain at a time — payments or onboarding first, the ledger last — running old and new in parallel until cutover is safe.
Why It Matters
Core replacement is historically the riskiest project in banking: multi-year, budget-hungry, and famous for catastrophic big-bang cutovers. The composable approach changes the risk profile rather than the ambition — each swap has a small blast radius, standardized service boundaries reduce vendor lock-in, and the core stops being a monolith and becomes an ecosystem. The standards do the heavy lifting: BIAN gives bank and vendors a shared vocabulary for what a capability is, and TOGAF keeps the multi-year effort governed instead of ad hoc.
Banking & Fintech Implications
A pragmatic sequence: map the current estate against the BIAN service landscape to expose duplication and gaps; pick the first domain to externalize based on business pain, not architectural purity; enforce API contracts at domain boundaries with BIAN's semantic APIs as the baseline; and use TOGAF's ADM to keep governance, architecture debt, and vendor decisions visible to the board. One constraint to plan for early: architects fluent in both TOGAF and BIAN are scarce, and the shared vocabulary is precisely what makes the model work.
My Take
'Coreless' is a deliberate provocation — the ledger never disappears; what disappears is the monolith's monopoly over change. The pattern I have seen work treats BIAN as the map, TOGAF as the operating rhythm, and the legacy core as a shrinking service domain rather than a system to be executed on a deadline. Frame the program as risk reduction — a smaller blast radius per change — and it gets funded; frame it as an IT rewrite and it dies in committee.