Cloud pricing term
What is data ingress?
Data ingress is data entering a provider or service boundary.
The expensive mistake
Reading free ingress as free networking. Uploading data can be free while the response, replication, load balancer, or path between zones is billed. Receiving bytes and later sending the same bytes back are two different pricing directions.
Where it appears on your bill
Internet ingress is often absent or shown as a zero-priced data-transfer line. Processing services and the later outbound path can appear as separate charges.
Worked example
Using the recorded AWS t4g.nano transfer terms, 250 GB uploaded from the internet is $0 for ingress. Sending 250 GB back out is max(0, 250 - 100) x $0.09 = $13.50. Free inbound traffic did not make the round trip free.
Example prices checked: