#Payments

Payment systems require idempotency, audit trails, and strict regulatory compliance. These articles cover UPI integration with NPCI, idempotent payment processing patterns, Kafka-based settlement pipelines, and the engineering controls needed to handle financial transactions reliably at scale.

54 posts tagged with payments. ← All posts

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Pratik Dhanave · ·6 min read

Mandates and Verifiable Credentials: Proving an Agent Was Authorized

When an AI agent spends your money, "the user said so" is not evidence. A signed mandate chain is.

A deep dive on the mandate chain as evidence: verifiable credentials (VCs), signing, the non-repudiable Intent→Cart→Payment chain, revocation and expiry, and why this replaces 'trust me, the user said so' with cryptograp…

#Agentic Commerce#Security#AI Agents#Identity#Payments#Fintech
Pratik Dhanave · ·6 min read

Card Authorization, Capture, and Clearing: One Transaction, Three Money States

How to model the card payment as a two-phase auth-then-capture flow plus a clearing tail — handling incremental auths, partial captures, reversals, expiry, and the auth-vs-settled reconciliation that trips up every ledger.

Teaches how to model the card transaction as a two-phase (auth then capture) plus clearing/settlement state machine, handling partial captures, incremental auths, auth expiry/reversal, and the auth-vs-settled amount reconciliation.

#Fintech#Payments#Cards#Financial Systems#Distributed Systems#Card Payments
Pratik Dhanave · ·6 min read

Integrating 3-D Secure 2 Without Breaking Your Checkout

Wiring the 3DS Server, Directory Server, and issuer ACS into a handshake that produces a cryptogram your authorization message can carry.

Teaches how to integrate 3-D Secure 2: the 3DS Server, Directory Server and issuer ACS handshake, frictionless vs challenge decisioning, device data collection, and liability-shift outcomes feeding the authorization.

#Fintech#Payments#Cards#Financial Systems#Distributed Systems#Card Payments
Pratik Dhanave · ·6 min read

Network Tokenization and How a Token Vault Shrinks Your PCI-DSS Scope

How a token vault and scheme-issued network tokens push the raw PAN out of your application systems, so most of your services fall out of PCI-DSS scope entirely.

Teaches how a token vault and network tokens (TR-31/EMV payment tokens) remove PAN from application systems, cutting PCI-DSS scope, and how token provisioning, cryptograms, and detokenization boundaries are architected.

#Fintech#Payments#Cards#Financial Systems#Distributed Systems#Card Payments
Pratik Dhanave · ·6 min read

Engineering SEPA: Mandates, Sequence Types, and the R-Transaction State Machine

How to engineer SEPA SCT and SDD flows: mandate lifecycle storage, pre-notification timing, FIRST/RCUR sequence types, and the R-transaction taxonomy modeled as an explicit state machine.

Teaches how to engineer SEPA SCT and SDD flows: mandate lifecycle storage, pre-notification timing, FIRST/RCUR sequence types, and the R-transaction taxonomy (reject/return/refund/reversal/revocation) as a state machine.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·6 min read

Threading a UETR Through SWIFT MT-to-MX Migration

How to parse legacy MT103/MT202 fields, map them to MX pacs equivalents during coexistence, and thread a gpi UETR end-to-end so a cross-border payment stays trackable across correspondent hops.

Teaches how to parse legacy MT103/MT202 fields, map them to MX pacs equivalents during coexistence, and thread a gpi UETR end-to-end so a cross-border payment is trackable across correspondent hops.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·6 min read

Building for Instant Payments: RTP, FedNow, and Request-for-Payment

How to engineer for 24x7 irrevocable instant credit — synchronous ISO 20022 messaging, request-for-payment flows, and idempotent liquidity checks with no batch cutoff.

Teaches how to build for 24x7 irrevocable instant credit: synchronous ISO 20022 request/response, request-for-payment (RfP) flows, credit-transfer timeouts, and idempotent liquidity checks at the rail with no batch cutoff.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·7 min read

The FIX Protocol: Engineering a Session and Order Gateway

The 40-year-old tag=value protocol still carrying most of the world's equity orders — and how to build an engine that survives a dropped connection.

How FIX session layer (logon, heartbeat, sequence-number gap-fill, resend) and application layer (NewOrderSingle, ExecutionReport) actually work, and how to build a resilient FIX engine.

#Fintech#Capital Markets#Rails#Trading#Financial Systems#Payment Rails#Payments
Pratik Dhanave · ·6 min read

Modeling ISO 20022 Payment Messages Without Losing Your Mind

How to treat pain, pacs, and camt as one typed, schema-driven domain instead of a pile of XML you concatenate by hand.

Teaches how to model, validate, and generate ISO 20022 XML payment messages (pain.001 initiation, pacs.008 interbank, camt.053 statements) with schema-driven typing, structured references, and idempotent message identifiers.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·6 min read

Building a Byte-Level ISO 8583 Codec for Card Authorization

A field-by-field guide to decoding bitmaps, data elements, and MTI so a raw TCP frame becomes a typed auth request you can trust.

Teaches how to build a byte-level ISO 8583 encoder/decoder: primary/secondary bitmaps, data-element (DE) field definitions, MTI parsing, and stan/RRN correlation for card authorization messaging.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·7 min read

Building a NACHA ACH File Processor: Records, Hash Totals, and Return Codes

Model the fixed-width record hierarchy, warehouse entries until their effective date, and turn R-series returns into automated re-presentment.

Teaches how to build a NACHA file processor: fixed-width file/batch/entry/addenda record hierarchy, hash totals, effective-entry-date windows, and handling R-series return/NOC codes with automated re-presentment logic.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·7 min read

Consuming APIs and Handling Webhooks

Talking to a payment rail is the least reliable part of your system. Treat every outbound call as fallible and every inbound webhook as hostile.

Talking to a payment rail is the least reliable part of your system. Treat every outbound call as fallible and reconcile on ambiguity; treat every inbound webhook as hostile — verify, dedupe, ack fast, and go read the truth.

#Fintech#Payments#Webhooks#Reliability#Distributed Systems#Financial Systems
Pratik Dhanave · ·7 min read

Executing Money Flows: Invariants, Reservations, and Overdrafts

A transfer is a state machine with money on the line. Model the states explicitly, reserve funds before you commit, and decide up front what an overdraft even means.

A transfer is a state machine with money on the line. Model the states explicitly, reserve funds before you commit, enforce invariants at every transition, and decide up front what an overdraft even means.

#Fintech#Payments#Reliability#State Machine#Distributed Systems#Financial Systems
Pratik Dhanave · ·6 min read

The Card Payment Actors Map: Who Actually Does What

One reference model of every party in a card transaction — cardholder, merchant, gateway, acquirer/processor, scheme, and issuer — and the settlement path that moves the real money back the other way.

One reference map of who does what in a card payment: cardholder, merchant, gateway, acquirer/processor, scheme, issuer, and the settlement return path.

#Fintech#Payments#Rails#Financial Systems#Distributed Systems#Payment Rails
Pratik Dhanave · ·7 min read

AP2 vs ACP vs x402 vs Network Tokens: How the Approaches Compare

A clear-eyed look at trust models, who signs what, rails, credential handling, and settlement — and why these four overlap more than they compete.

A clear-eyed comparison across trust model, who signs what, payment rails supported, credential handling, settlement, and best-fit use cases.

#Agentic Commerce#Payments#Fintech#Crypto#AI Agents#Distributed Systems#Financial Systems#Cryptocurrency
Pratik Dhanave · ·8 min read

Building an Agent-Ready Merchant

The surface a store must expose when the buyer is an AI agent, not a browser — and why it is the fintech reliability playbook wearing a new hat.

What a store must expose to sell to agents: a machine-readable product feed/catalog, agentic checkout endpoints, acceptance of delegated payment tokens, idempotency keys for retried agent calls, webhooks for async status…

#Agentic Commerce#Payments#Architecture#Fintech#AI Agents#Distributed Systems#Financial Systems
Pratik Dhanave · ·7 min read

"My Agent Did It": Fraud, Disputes, and Liability in Agentic Commerce

When software holds the card and clicks "buy," the old questions — was this the cardholder, did they mean to, who pays if not — all get harder to answer.

The new fraud surface: prompt injection turning a shopping agent into an attacker's buyer, hijacked delegated credentials (Visa saw ~450% more dark-web 'AI Agent' chatter in H1 2026), and disputes when an agent acted on…

#Agentic Commerce#Fraud#Risk#Compliance#AI Agents#Payments#Fintech#Governance
Pratik Dhanave · ·7 min read

The Agentic Checkout Flow, End to End

How an AI agent turns a shopper's intent into a settled purchase, and where ACP and AP2 plug into the same eight-stage skeleton.

A complete walkthrough: product discovery via an AI surface → cart assembly → user approval/mandate → delegated payment token → merchant checkout → authorization → fulfillment → receipts/webhooks.

#Agentic Commerce#Payments#AI Agents#Fintech#Distributed Systems#Financial Systems
Pratik Dhanave · ·5 min read

Building a Dunning and Retry Engine for Failed Payments

How decline-code classification, backoff scheduling, retry budgets, and network-token refresh recover subscription revenue without hammering the rails.

Teaches how to build a smart retry/dunning system: decline-code classification (hard vs soft), backoff and retry-window scheduling, retry-budget limits, and network-token refresh to recover subscription revenue.

#Fintech#Payments#Reliability#Financial Systems#Distributed Systems
Pratik Dhanave · ·6 min read

Building Marketplace Split Payments and Connected Payouts

Architecting platform balances, commission splits, delayed payouts, and negative-balance recovery without ever losing a cent.

Teaches how to architect marketplace money movement: platform vs connected-account balances, fee/commission splits, delayed payouts, negative-balance handling, and merchant-of-record vs facilitator models.

#Fintech#Payments#Reliability#Financial Systems#Distributed Systems
Pratik Dhanave · ·6 min read

Engineering Escrow: Conditional Hold and Release with Double-Entry Safety

How to build escrow and conditional hold/release — segregated ledger accounts, release conditions and approvals, partial releases, and expiry auto-refund that never strand money.

Teaches how to build escrow and conditional hold/release: segregated escrow ledger accounts, release conditions/approvals, partial releases, and expiry auto-refund with double-entry safety.

#Fintech#Payments#Reliability#Financial Systems#Distributed Systems
Pratik Dhanave · ·7 min read

Card Networks Enter Agentic Commerce: Visa Intelligent Commerce and Mastercard Agent Pay

How Visa and Mastercard are reshaping tokenization so an AI agent can pay on your behalf — with scoped credentials, agent-aware identity, and the network doing what it has always done: authenticate, authorize, tokenize.

How the card networks are adapting tokenization for agents.

#Agentic Commerce#Cards#Payments#Security#AI Agents#Fintech#Card Payments#Distributed Systems
Pratik Dhanave · ·7 min read

RTGS vs Deferred Net Settlement

Two ways to move interbank money, and the engineering tradeoff that decides which one you build: settle every payment gross and pay in liquidity, or net at a window and carry settlement risk.

Teaches the engineering tradeoffs between gross real-time settlement and deferred net settlement: liquidity vs finality, queue/gridlock resolution in RTGS, and settlement-risk windows in DNS.

#Fintech#Payments#Settlement#Financial Systems#Distributed Systems
Pratik Dhanave · ·6 min read

Payment-versus-Payment: Settling FX Without Principal Risk

How matched-leg submission, net pay-in scheduling, and conditional simultaneous settlement remove Herstatt risk from cross-currency trades.

Teaches how payment-versus-payment settlement eliminates Herstatt (principal) risk in FX: matched trade submission, pay-in schedules, simultaneous conditional settlement, and pay-out with net funding.

#Fintech#Payments#Settlement#Financial Systems#Distributed Systems
Pratik Dhanave · ·6 min read

Building a Deterministic Interchange Fee Engine

Turn card transaction attributes into interchange, scheme, and markup lines that reconcile to the cent.

Teaches how to build a deterministic fee engine that classifies each transaction into an interchange category (regulated debit, rewards, CPS qualification) and computes interchange + scheme + acquirer markup for merchant statements.

#Fintech#Payments#Cards#Financial Systems#Distributed Systems#Card Payments
Pratik Dhanave · ·6 min read

Designing a Netting Engine That Collapses Gross Obligations Into Minimal Settlement

How to turn thousands of gross obligations into the fewest net positions per counterparty — with deterministic cutoff snapshots, netting cycles, and net-debit-cap enforcement.

Teaches how to build a netting engine that collapses many gross obligations into minimal net settlement positions per counterparty, handling netting cycles, cutoff snapshots, and net-debit-cap enforcement.

#Fintech#Payments#Settlement#Financial Systems#Distributed Systems
Pratik Dhanave · ·6 min read

Modeling Card Chargebacks as a State Machine

Modeling the full card dispute lifecycle with reason codes, evidence deadlines, representment, arbitration, and provisional-credit ledger entries at every transition.

Teaches how to model the full card dispute lifecycle as a state machine with reason codes, evidence deadlines, representment, pre-arbitration and arbitration, and provisional-credit ledger entries at each transition.

#Fintech#Payments#Cards#Financial Systems#Distributed Systems#Card Payments

All posts on this site are written by Pratik Dhanave, an Agentic AI Architect with 7+ years building production distributed systems, multi-agent AI platforms, and cloud-native infrastructure. About the author → Each article includes working code, architecture diagrams, and references to the specific frameworks and standards discussed. Browse all posts or explore related topics using the tag cloud above.