Lakshya

Banking & Capital Markets Systems · Chapter 1 of 13

How a bank's stack actually decomposes

Seven layers, and why 'core banking' means three different things depending on who is saying it.

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Banking technology is unusually legible once you see the layering, and unusually confusing before that — mostly because one term, core banking, gets used for three different things in the same conversation.

WHERE THE WORK ACTUALLY IS — “CORE BANKING” IS ONE LAYER OF SEVEN CHANNELSapp, net banking, branch, ATM, call centrebought or built — and the answer differs per business lineORIGINATIONonboarding, KYC, loan originationLOS vendors + the bureau pullCORE BANKINGthe ledger: accounts, balances, posting, GLFinacle · BaNCS · FLEXCUBE · TemenosPAYMENTS & SWITCHISO-8583 routing, card managementthe switch is NOT the same thing as NFSTREASURY & MARKETSFX, rates, securities, custodyMurex · Calypso · BaNCS — and CCIL underneath all of itRISK & AMLlimits, ECL, transaction monitoringOFSAA · Actimize — DETECTIONREGULATORY REPORTINGreturns to RBI and SEBIADF → CIMS — LINEAGE, a different problem “CORE BANKING” MEANS THREE DIFFERENT THINGS AND PEOPLE SWITCH BETWEEN THEM MID-SENTENCE the ledger itself · the vendor SUITE sold around it (payments, trade, wealth as licensable modules) · the whole bank stack, colloquially
Most of the hiring is not in the middle box. The ledger is the smallest, oldest and most conservative layer; the work is in the layers wrapped around it.

The three meanings, because you will hear all of them

  • The ledger. Accounts, balances, posting, the general ledger, interest accrual, end-of-day. This is what a core banking system is, strictly.
  • The vendor suite sold around it. Finacle, BaNCS and FLEXCUBE are all sold as families — core, plus payments, trade finance, wealth, treasury, digital engagement as separately licensable modules on a shared customer and account master. A bank can run one vendor's core and a different vendor's wealth module, and several do.
  • The whole stack, colloquially. “We're replacing core banking” often means a programme touching channels, origination and reporting as well.

The distinction matters in an interview because the three have completely different job shapes. Ledger work is COBOL-adjacent conservatism, batch windows and reconciliation. Suite-module work is configuration and integration. Programme work is migration and coexistence, which is where most of the actual difficulty lives.

The two layers people conflate at the bottom

Risk and AML is a detection problem. Regulatory reporting is a lineage problem. They sit next to each other on the diagram and get merged in job titles, but transaction monitoring is about finding anomalies in behaviour, while reporting to the regulator is about extracting the same number the same way every time, with a defensible trail back to the ledger. Different skills, different tools, different failure modes — and the second one is much larger than outsiders assume.

A note on how this book is sourced, because it is different from the rest of the site

Every other book here is written from a job-posting corpus. This one is not, and it cannot be — the corpus contains 184 employers and not one of them is a bank. Searching all 4,556 full job descriptions in it returns zero mentions of Finacle, BaNCS, FLEXCUBE, Temenos, Murex, Calypso, OFSAA, Aladdin, SimCorp, UPI, RTGS (Real Time Gross Settlement) or SEBI.

So this book is written from regulator and exchange publications, bank annual reports and disclosures, and dated vendor announcements — and it says out loud, chapter by chapter, which claims are sourced and which are not.

That is not a disclaimer. It is the single most useful thing this book can teach you about the field: a very large amount of what circulates as fact about who runs what is unsourced, and the confident lists online are citing each other rather than a bank.

Check yourself

What are the three meanings of 'core banking'?The ledger itself; the vendor suite sold around it (payments, trade, wealth as licensable modules); and the whole bank stack colloquially. They are three different jobs.
Can a bank run two vendors?Yes, and several do — one vendor's core with another's wealth or digital module. HDFC runs FLEXCUBE and Finware for core, Finacle for wealth, and Backbase for retail digital.
What is the difference between AML and regulatory reporting?AML is detection — anomalies in behaviour. Regulatory reporting is lineage — the same number extracted the same way every time with a defensible trail to the ledger. Different tools, different failure modes.
Why is this book sourced differently from the rest of the site?The job-posting corpus contains no banks — 184 employers, zero. So this is written from regulator publications, annual reports and dated vendor announcements, with the sourcing stated per claim.
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