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svg]:px-3 !p-0" href="/blog"> Back to blog3 Costly Database Failures That Changed Software Engineering Forever<br>Discover three real-world database failures that cost companies hundreds of millions of dollars. Learn how Samsung Securities, TSB Bank, and GitLab transformed the way engineers approach data validation, database migrations, backups, and disaster recovery.
StackRenderTamani Karim<br>4 minutes read
Database failures rarely make headlines, until they cost companies millions of dollars.
From accidentally creating 2.8 billion phantom shares , to a failed banking migration that locked 1.9 million customers out of their accounts, to a database outage that took down one of the world's largest DevOps platforms, these incidents reshaped the way modern software is built.
In this article, we'll examine three real-world database failures, what went wrong, the impact they had, and the engineering lessons they continue to teach teams building critical systems today.
Samsung Securities (2018)
In April 2018, Samsung Securities intended to distribute dividends to its employees. Due to a system error, the platform issued billions of company shares instead of the intended cash dividends. Employees briefly had access to shares that should never have existed, and some sold them before the mistake was discovered.
The Error
The 2018 Samsung Securities incident was triggered by a simple fat-finger error that caused the system to mistakenly distribute 2.8 billion phantom shares , worth approximately $105 billion , to around 2,000 employees participating in the company's employee stock ownership plan.
The intention was to pay each employee a cash dividend of 1,000 South Korean won (approximately $0.93 ). Instead, an employee accidentally entered 1,000 shares rather than 1,000 won , causing the system to create billions of shares out of thin air and credit them directly to employees' accounts.
The Impact
Before the mistake could be corrected, 16 employees sold a portion of the phantom shares , causing Samsung Securities' stock price to plunge by nearly 12% during intraday trading.
The incident triggered regulatory investigations, exposed weaknesses in the company's internal controls, and ultimately cost Samsung Securities more than $105 million in penalties, compensation, and legal settlements.
The Lesson
Following the incident, Samsung Securities implemented several corrective measures that have since become valuable lessons for software engineers building financial systems:
Two-Person Rule: Critical corporate actions and large ledger adjustments now require verification and approval from multiple authorized employees before they can be executed.
Hard Caps and Limits: System-enforced safeguards and constraints prevent the issuance of shares beyond the company's authorized or outstanding share limits.
Automated Anomaly Detection: Real-time monitoring and circuit breakers automatically detect abnormal asset creation and freeze suspicious transactions before they can impact the market.
TSB Bank (2018)
In April 2018, TSB Bank attempted one of the largest banking technology migrations in UK history, moving 5.2 million customers from its former parent company's infrastructure to a new in-house banking platform. Instead of delivering a seamless transition, the migration triggered weeks of outages that left customers unable to access their accounts, make payments, or use online banking services, making it one of the most significant IT failures in the banking industry.
The Error
The migration failed due to a combination of technical and project management mistakes. TSB attempted to migrate its banking platform under an aggressive timeline while simultaneously upgrading the core banking system, increasing the complexity and risk of the project.
Independent reviews also identified poor coordination across more than 1,400 team members and 70+ third-party suppliers , insufficient end-to-end data testing, and the absence of a dedicated data testing and automation strategy. Together, these failures turned what should have been a controlled migration into one of the largest banking IT failures in UK history.
The Impact
The migration failure affected 1.9 million customers , leaving many unable to access their accounts for weeks. TSB ultimately reported £330 million in costs related to the incident, including customer compensation, remediation efforts, and regulatory penalties, making it one of the most expensive banking IT failures in UK history.
The Lesson
The TSB incident demonstrated that successful database migrations require far more than moving data from one system to another. They demand careful planning, realistic timelines, comprehensive testing, and well-defined rollback...