Systems and methods are described for balancing workloads and reliably delivering data to a plurality of indexing systems in a data intake and query system. A topic-based indexing system load balancer may receive event data from various data sources, each of which may be associated with a topic. The event data may be entirely unparsed, unparsed but divided into events, or parsed into events. The topic-based indexing system load balancer may distribute the received event data on a per-topic or per-event basis to a set of indexing systems, and may distribute topics and events based on the volume received. Unparsed data may be divided into portions, and the topic-based indexing system load balancer may ensure that portions data associated with the same topic are delivered to the same indexer so that events split between two portions may be recombined and indexed.