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Data quality · Contracts & Ops

Data freshness

Easyquality-13
freshnessSLAloaded_atevent_time

Question

What is data freshness, and how do you measure it?

Solution

Data freshness is how up to date a dataset is relative to the source or to "now." Stale data is a quality failure even when every row is perfectly accurate.

How teams measure it

Common age formulas:

freshness_age = now - max(event_time)      # business time lag
freshness_age = now - max(loaded_at)       # pipeline arrival lag

Example: if max(ordered_at) in fct_orders is 3 hours ago and the SLA is 1 hour, freshness is breached.

Related checks

  • Source freshness (raw landing stopped updating)
  • Model freshness (transform did not run)
  • Partition arrival (today's partition missing)
SLA target: fct_orders age <= 60 minutes
source max time: 10:00
warehouse max:   12:30  -> BREACH (150 minutes)

Design note

Needed freshness depends on the use case. Fraud may need minutes; weekly exec reporting may tolerate a day.

Interview tip: Define freshness as data age, show now - max(timestamp), and separate source lag from transform lag.

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