A method to efficiently checkpoint and reconstruct an in-memory index associated with a log-structured object store includes enabling asynchronous write operations to occur to a log-structured object store. The log-structured object store utilizes an in-memory index to access objects therein. The method further enables checkpoint operations to occur to the log-structured object store without pausing the asynchronous write operations. When initiating checkpoint operations, the method establishes a “begin checkpoint” marker on the log-structured object store. This “begin checkpoint” marker is configured to point to an oldest known log location recorded in the in-memory index. In the event the in-memory index is lost, the method reconstructs the in-memory index by analyzing the log-structured object store starting from the oldest known log location. A corresponding system and computer program product are also disclosed and claimed herein.