The Situation
The client runs a family office managing investment portfolios across multiple brokerage accounts. He was building an automated investment audit system in n8n that would pull portfolio data from a brokerage API, normalize it, and generate reconciliation reports. Two technical issues had him stuck for weeks.
The first was an HMAC-SHA256 authentication failure where the cryptographic signature his workflow generated didn't match what the API expected. The second was a data processing issue where n8n was handling portfolio arrays item-by-item instead of as a batch, producing incorrect reconciliation results.
What We Built
The initial engagement started with a diagnosis. We identified both issues from the client's description, explained exactly what was wrong, and told him to try the fixes himself. He came back and asked for a long-term partnership instead.
The ongoing build expanded into a multi-phase investment operations system: automated daily portfolio pulls across all accounts, transaction reconciliation against expected allocations, discrepancy flagging with configurable thresholds, reporting dashboards, and an alert system for positions that drift outside target ranges.
Results
HMAC-SHA256 authentication resolved. Data processing corrected (batch mode for array handling). Daily automated portfolio pulls across multiple accounts. Automated reconciliation reports. Initial debug turned into $15,000-$25,000 multi-phase engagement.
Tech Stack
What Made This Work
Before quoting a price, we diagnosed both issues in plain English and told the client to try the fixes himself. Giving away the answer proved we understood the problem in minutes when he'd been stuck for weeks. That gap between the free diagnosis and the full system architecture is what turned a $2,500 debug into a long-term partnership.