The dYdX Chain, a decentralized derivatives exchange protocol, experienced a significant outage lasting approximately 5 hours due to a software upgrade issue. The problem began early on Monday, with the chain halting operations amid the v4.0.0 upgrade. Engineers were dispatched to debug the issue, which persisted for several hours, with the outage commencing at 6:50 a.m. UTC. The dYdX operations team aimed to resolve the problem within a few hours, marking the exchange's first major outage since launching its fourth version. Eventually, the chain resumed operations and began producing blocks again after a critical update to v4.0.2 was implemented to fix a bug in the original v4.0.0 upgrade.