01 · Architecture
Payment middleware design
Designed event-driven microservices architecture for card clearing webhooks.
120M+
Transactions cleared
99.999%
API uptime SLA
Certified
Visa / Mastercard
Overview
The project
in context.
Opensparkz re-engineers loyalty programs by linking rewards directly to payment cards at the network level without requiring merchant terminal upgrades. StartxLabs contributed to building high-performance PCI-compliant API webhooks and real-time transaction matching engines.
Zero-friction loyalty APIPCI-DSS Level 1Sub-100ms matching
The challenge
What was
blocking progress.
Traditional loyalty programs required costly hardware upgrades or staff training at retail point-of-sale (POS) terminals.
01
Handling high-throughput transaction webhooks from Visa and Mastercard networks
02
Sub-100ms offer matching latency to enable instant consumer notifications
03
Strict PCI-DSS Level 1 compliance for encrypted payment token handling
04
Developer API portal for merchant partners to configure loyalty rules dynamically
Our solution
How we
approached it.
We engineered high-concurrency payment middleware microservices with real-time offer matching.
01
Built resilient API gateway processing thousands of concurrent card clearing events
02
Implemented zero-friction card-linking backend bypassing POS terminal requirements
03
Created developer portal with API key management, webhooks, and sandbox testing
04
Enforced PCI-DSS security tunnels for handling payment card tokens
Delivery process
From discovery
to durable outcomes.
02 · Security
PCI-DSS tokenization
Implemented hardware security module (HSM) integrations for card tokens.
03 · Build
Rules engine delivery
Shipped sub-100ms merchant offer matching and cashback settlement engine.
04 · Validate
Card scheme certification
Validated API integrations with Visa and Mastercard network standards.
Product gallery
Screens and surfaces
from the build.
Selected visuals from Opensparkz - product UI, mobile flows, and delivery artifacts from the engagement.
Scope of work
What we owned.
Fintech API engineering
Payment middleware
PCI compliance
Developer portal
Key deliverables
Opensparkz card-linking API gateway
Real-time transaction matching engine
Developer portal & sandbox
Merchant offer configuration suite
Capabilities & stack
GoNode.jsKafkaRedisAWS HSMPCI-DSSFintechAPI platformPaymentsMiddleware
Impact
What changed
after launch.
Outcomes from the Opensparkz engagement - measured in how teams operated, how the product matured, and what became possible next.
01
Processed over 120 million card-linked payment transactions
02
Achieved 99.999% platform uptime for real-time payment webhook processing
03
Fully certified across Visa and Mastercard payment network standards
04
Eliminated POS hardware integration costs for hundreds of merchant brands
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