Achieving multi-lead electrocardiography (ECG) in consumer-grade wearables remains challenging, as most devices provide only a few electrodes and cannot capture spatially diverse cardiac signals. Conventional 12-lead ECG, while clinically standard, requires ten electrodes across the body, confining its use to medical environments. We present EarSleeve, a modular dual-electrode eartip sleeve that transforms off-the-shelf earphones into a 12-lead ECG sensing platform through a human-in-the-loop design. Each sleeve embeds two conductive electrodes and electrically links both sides to form a four-electrode configuration. EarSleeve simultaneously records six limb leads and reconstructs 12-lead–equivalent ECG signals by sequentially contacting standard chest locations. In a 12-user study, EarSleeve captures clear ECG waveforms across all leads and is evaluated against an FDA-cleared reference. Results demonstrate the feasibility of reconstructing 12-lead–equivalent ECG signals using a minimum-electrode configuration under controlled conditions. To our knowledge, EarSleeve is the first system to achieve this with off-the-shelf earphones.

Software errors and incidents are inevitable in web-based applications. Scalability challenges, increasing demand, and ongoing code changes can contribute to such failures. As software architectures evolve rapidly, understanding how and why incidents occur is crucial for enhancing system reliability. In this study, we introduce Carbon Health’s software stack, share our microservices journey, and analyze 107 incidents. Based on these incidents, we share insights and lessons learned on microservice decomposition. Finally, we suggest that starting with monolithic modularization as an initial step toward microservice decomposition may help reduce incidents and contribute to building more resilient software.