Question: What is P50 latency?

Answer

"P50 latency" refers to the median latency in a distribution of latencies, meaning that 50% of the data points are below this value. In the context of databases or web services, it's used to understand the performance characteristic - specifically how long it takes to complete a request.

When looking at latency distributions, there could be a large spread from the lowest to the highest values. This is why using the average might not give an accurate picture of what users typically experience. Median (P50) is less sensitive to outliers and thus can provide a more representative measure.

If you have a list of individual latencies, you could calculate P50 latency in Python using the numpy library like so:

import numpy as np

latencies = [1, 2, 3, 4, 5] # replace with your data
p50_latency = np.percentile(latencies, 50)

Alternatively, many monitoring tools like Prometheus, Datadog, or New Relic provide built-in functions to calculate percentile-based metrics such as P50, P90, P95, P99 which represent different percentiles in the latency distribution.