Database audit and transaction logs are fundamental to forensic investigations, but they are vulnerable to tampering by privileged attackers. Malicious insiders or external threats with administrative access can alter, purge, or temporarily disable logging mechanisms, creating significant blind spots and rendering disk-based records unreliable. Memory analysis offers a vital alternative, providing investigators direct access to volatile artifacts that represent a ground-truth source of recent user activity, even when log files have been compromised. This paper introduces MemTraceDB, a tool that reconstructs user activity timelines by analyzing raw memory snapshots from the MySQL database process. MemTraceDB utilizes a novel algorithm, ActiviTimeTrace, to systematically extract and correlate forensic artifacts such as user connections and executed queries. Through a series of experiments, I demonstrate MemTraceDB's effectiveness and reveal a critical empirical finding: the MySQL query stack has a finite operational capacity of approximately 9,997 queries. This discovery allows me to establish a practical, data-driven formula for determining the optimal frequency for memory snapshot collection, providing a clear, actionable guideline for investigators. The result is a forensically-sound reconstruction of user activity, independent of compromised disk-based logs.