With years working directly with core banking and consult banks. I’ve learned that if you strip away all the vendor branding whatever who they are T24, Thoughmachine, Fiserv,... all key components you need to know boils down to the exact 5 components, remaining can be expanded and compact depend on bank size and their core business model
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The Ledger Everything begins and ends with double-entry: accounts, balances, and entries. Every other components exists to feed data into the ledger or extract statements from it. In a common web app, a stale read in most case is acceptable for performance trade-off but in a banking ledger, a stale read is an incorrect balance and most of the case is not acceptable . A wrong balance is far worse than a correct balance delivered slightly slower. "Eventually consistent" isn't never a choice here
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Product Catalog This is where deposits, loans, interest accruals, fee schedules, and maturities are provisioned. This engine determines whether launching a new savings product takes 2 weeks of configuration or a long six-month delivery cycle. Whenever evaluate a vendor or a new core, alway do the test: "Show me a product one of your existing clients built and deployed without paying for your professional services." The vendor's response and the length of the pause before they answer - tells me everything I need to know about roadmap velocity and how much dependent i may involve if choosing this vendor
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The Customer Master Managing customer identity, legal relationships, and consents. In older legacy cores, customer data is completely wired to individual account records. Modern one isolate the Customer Master so a client regardless of how many products they hold, and they tend to collect as much as customer data features nowaday to "understand" the customer and offer the right product to them
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Batch Engine The nightly close, interest calculation, fee calculation, and statement runs form the core’s operational day to day. Most customer-facing cutoff times are just the batch window to do async job, cleaning, reconcilation, check gates, etc. In modern core, they leverage event-driven to optimize this processing SLA significantly, but end-of-day batch remains a reality for most of banking operations.
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Interfaces Customer channels, employee channel, payment gateways, risk engines, and reporting platforms all connect through this layer. Usually legacy core provide only web app to customer and same for banker to do daily operation with a very limitted of functionality. Nowaday, bunch of bank build their digital layer on top of the core banking or even buy from vendor the digital offering. This eventually become a norm for both internal and customer facing to speedup and digitalize the experiences.
That's basically all you need to know about core banking 101 and a high level understanding of what happen under the hood when you as a customer do a money tranfer to others