The $2,300 Weekend: When Fallback Routing Goes Wrong in AI Gateways

Last month, a misconfigured fallback route in an AI gateway caused a $40/month API bill to skyrocket to $2,300 in just 48 hours. This happened when the primary model, DeepSeek-V3, was set up with a fallback to GPT-4o. The issue was that the fallback was overly sensitive, causing it to get triggered too easily, leading to excessive costs. This incident highlights a common mistake in setting up AI routing systems and underscores the importance of careful configuration to avoid unexpected expenses.