Incident Library

Organisation

Heroku

Heroku · heroku

5 cases · 2017 to 2025

Root cause Software defect2Breaking change in an upgrade2DNS or network fault1
Component Cloud load balancer2Database2Authoritative DNS servers and records1Host routes and routing rules1Service discovery1Telemetry agent1
Contributing factor Monitoring blind spot2Unverified assumption1Circular dependency1Limited debug access1Unrepresentative staging1Unpinned version1
Symptom High error rate3High latency2Service outage2Load imbalance2Intermittent timeouts1Memory pressure1Network unreachable1Stale endpoint routing1

Cases

  1. IL-0352 Heroku Router 2.0 spread HTTP requests unevenly across dynos for four days, causing latency and timeoutsHeroku · 2025

    Root cause Software defect

  2. IL-0227 Most Heroku dynos in Private Spaces lost outbound connectivity after an automated OS update restarted host networkingHeroku · 2025

    Root cause Breaking change in an upgrade

  3. IL-0373 Heroku Postgres Essential-tier databases in the EU region ran out of memory and refused connections, twice in four daysHeroku · 2024

    Root cause Software defect

  4. IL-0372 Heroku apps could not connect to about 1% of hobby-tier Postgres databases after the databases' host names changedHeroku · 2021

    Root cause Breaking change in an upgrade

  5. IL-0351 Heroku apps in the EU and US had slow and failed requests as DNS round-robin sent traffic to single router hostsHeroku · 2017

    Root cause DNS or network fault