Apache Druid vs. Time-Series Databases

by Rick Bilodeau · June 11, 2019

We occasionally get questions regarding how Apache Druid differs from time-series databases (TSDB) such as InfluxDB or Prometheus, and when to use each technology. This short post serves to help answer these questions.

The most important thing to keep in mind is that Druid is not a TSDB and the comparisons aren’t always apples to apples. Although Druid draws ideas from a number of TSDB concepts, it is designed for a wider range of analytic use cases than those for which a TSDB is usually employed.

Specifically, Druid is primarily deployed to:

  • Power user-facing analytics applications that require low latency (sub-second) queries.
  • Enable ad-hoc and exploratory analytics, where numerous iterative queries are issued to understand a data pattern or anomaly.
  • Quickly ingest (up to millions of events per second) complex events (data points with hundreds of fields).
  • Support concurrent queries from hundreds or thousands of concurrent users.
  • Answer complex OLAP queries on very large data sets.

Most TSDBs are designed to collect and aggregate metrics from servers and devices. Metrics are series of timestamps, tags or attributes, and numbers. TSDBs typically store each metric series individually, partition/shard each series around time, and provide query capabilities for aggregating numbers. TSDBs work great if your use case is to simply aggregate numbers/counters, and if you don’t require any complex analytics for each series.

If you do need analytics – for instance you want to group on non-time-based tags and attributes, or want to slice and dice on your metrics arbitrarily, you’ll need a database that is architecturally designed for the workflow. For example, consider a use case with server metrics. If you want to simply compute the average network latency of your servers across your data center, most TSDBs would serve your use case well. However, if you also want to perform complex slice and dice operations against multiple dimensions, such as computing the 95th percentile network latency of your data centers, grouped on data center location and server type, and filtered by a specific set of IPs, TSDBs can struggle with these queries at scale.

Druid is a real-time analytics database that not only incorporates architecture designs from TSDBs such as time-based partitioning and fast aggregation, but also includes ideas from search systems and data warehouses, making it a great fit for all types of event-driven data. Druid is fundamentally an OLAP engine at heart, albeit one designed for more modern, event-driven architectures.

Because Druid also draws inspiration from data warehouses, it is able to perform complex analytic queries better due to its architecture, which offers the following advantages over those of a typical TSDB: Column oriented storage, ideal for multi-dimensional groupBys on columns that are not time-based. Fast search and filter through inverted indexes, for fast ad-hoc slice and dice. Minimal schema design, and native support for semi-structured and nested data.

To summarize, Druid tends to perform better on large data sets that require grouping and filtering on many columns by many concurrent users.

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