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Meta·Software Engineer·Onsite - System Design / Architecture·Senior

Senior
May 2026

Summary

Meta system design round, one question about chargeback transaction flow to Visa. Pretty focused scope but there's a lot hiding underneath the surface once you start pulling on the reliability and ordering requirements.

Questions Asked (1)

Q1

Design a system to send chargeback transactions to Visa.

System DesignAPI & IntegrationsTechnical Trade-offs
Author's notes

I went straight to the happy path and started sketching a simple event queue feeding into an outbound API.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements: chargeback types, volume, latency, and compliance needs. Then design a reliable, idempotent pipeline that validates, formats, and transmits chargeback data to Visa's API, with retries, monitoring, and reconciliation. Discuss trade-offs between synchronous vs asynchronous processing and data consistency.

Pro tip: Emphasize idempotency and exactly-once semantics, as duplicate chargebacks can cause financial discrepancies. Also, mention the importance of audit trails and compliance with PCI DSS and Visa's specific chargeback rules.

1. Clarify Requirements

Ask about chargeback volume, latency requirements, data sources, and Visa's API specifications. Understand compliance and security constraints.

2. High-Level Architecture

Propose a pipeline: ingest chargeback events, validate and enrich data, queue for processing, and send to Visa via their API. Include retry and dead-letter queues.

3. Data Model and API Integration

Define the chargeback data model and map it to Visa's API format. Discuss authentication, rate limiting, and error handling for API calls.

4. Reliability and Scalability

Ensure idempotency with unique keys, implement retries with exponential backoff, and use a distributed queue for scalability. Consider partitioning by merchant or transaction ID.

5. Monitoring and Reconciliation

Set up logging, metrics, and alerts for failures. Implement reconciliation to match sent chargebacks with Visa's responses and handle discrepancies.

Key Points to Mention

  • Idempotency and exactly-once processing to avoid duplicate chargebacks
  • Asynchronous processing with message queues for reliability and scalability
  • Retry mechanisms with exponential backoff and dead-letter queues
  • Compliance with PCI DSS and Visa's chargeback rules
  • Monitoring, alerting, and reconciliation for operational visibility
  • Trade-offs between consistency, latency, and throughput

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.