IL-0309 Preset · 2026-04-13databaseaws
Preset's RDS PostgreSQL 14.7 to 17.9 upgrade in US East 1 ran out of storage and took Superset down for six hours
Preset planned to upgrade every RDS PostgreSQL instance in production US East 1 from 14.7 to 17.9. The API Gateway and Examples instances finished by 04:18 EDT, but the primary database instance went through 38 minutes of pre-upgrade checks and then a pre-upgrade snapshot that ran for about 4.5 hours. Before a major version upgrade, RDS takes a full, non-incremental snapshot regardless of any snapshots that already exist, while the daily automated snapshots of this instance are incremental, which is why they had always been quick. Preset states that S3 snapshot throughput is an AWS-side limit of about 30–45MB/s regardless of the EBS volume's provisioned throughput, so a full snapshot of 440GB at about 40MB/s takes at least about 3 hours, and that this limit only shows during full snapshots, which are rare in normal operation.
The volume was 500GB, with about 440GB used and about 64GB free at the start. During the long snapshot the remaining ~60GB of free storage was taken by the snapshot's temporary files and metadata, by pg_upgrade working files and output logs, and by WAL that accumulated while the snapshot ran. When free storage reached zero, the upgrade failed at 09:37 EDT. The pre-upgrade snapshot completed at 10:10, and AWS rolled the instance back automatically to its pre-upgrade state on PostgreSQL 14.15 without restoring from a snapshot. The instance restarted at 10:13 in a consistent state with no data loss and no manual intervention, and a post-rollback snapshot ran automatically until 11:29.
- Severity
- –
- Scope
- Superset was unavailable for about 6 hours for all customers on the us2a production deployment; no data was lost or corrupted
- Users affected
- All customers on the us2a production deployment
- Region
- US East 1
- Time to detect
- –
- Time to resolve
- 6h
Symptoms
A planned major version upgrade of Preset's production RDS PostgreSQL instances in US East 1, from 14.7 to 17.9, ran far past its maintenance window, and all customers on the us2a deployment could not reach Superset. After more than five hours the upgrade failed with "Postgres cluster is in a state where pg_upgrade cannot be completed successfully."
The upgrade began with a ModifyDBInstance API call at 04:12 EDT. The pre-upgrade compatibility checks on the primary instance took 38 minutes, and at 04:51 the instance shut down and a snapshot started. At 05:28 the snapshot showed sequential reads at about 45MB/s with writes near zero. At 08:00 I/O throughput rose to about 55MB/s and CPU jumped to about 70%, which looked like a change of phase, and at 09:22 reads fell to near zero while writes rose to 130MB/s, which looked like the instance recovering. At 09:37 RDS reported the upgrade as failed.
Nothing before the window pointed to a long snapshot. The same upgrade had finished in under 15 minutes on sandbox, staging and several other production regions, and the daily automated snapshots of this instance always took 10–15 minutes. An AWS support ticket opened at 07:26 got the reply at 08:36 that the upgrade was progressing normally, that no intervention was possible and that there was no ETA.
Symptom Service outageUpgrade stall
Root cause
Root cause Capacity exhaustion
- Trigger
- A planned major version upgrade of all RDS instances in production US East 1 from PostgreSQL 14.7 to 17.9, started with a ModifyDBInstance API call at 04:12 EDT.
Detection
The planned upgrade was being watched as it ran: the snapshot's I/O was observed at 05:28 EDT, the incident was posted on the status page at 06:00 EDT and an AWS support ticket was opened at 07:26 EDT.
Remediation
- AWS rolled the failed upgrade back automatically, and the instance restarted on PostgreSQL 14.15 at 10:13 EDT
Action items
- Rehearse the upgrade against a full production-scale dataset to check storage and timing estimates before any future major version upgrade
Lessons
Preset learned that RDS takes a full, non-incremental snapshot before a major version upgrade, so the duration of the daily incremental snapshots and of the upgrades in other regions said nothing about how long the pre-upgrade snapshot would take on this instance. The S3 snapshot throughput limit of about 30–45MB/s only becomes visible during such full snapshots, which are rare in normal operation.
Sources
- https://status.preset.io/incidents/01KP34GXYRB4A4RHNH1Y43KSWM/write-up · official-status
Related cases
IL-0334Instapaper's RDS MySQL bookmarks table hit the 2TB ext3 file size limit, inserts failed and the service went downInstapaper · 2017same root cause · shared Database, Database backups and snapshots
IL-0450Oracle RAC commits behind order APIs kept waiting over 0.1 s on log file sync while average host CPU had headroomToss Securities · 2026same root cause · shared Database
IL-0553CircleCI's orchestration database filled its transaction log volume, and no workflows or jobs started for 50 minutesCircleCI · 2026same root cause · shared Database
IL-0379InfluxDB Cloud queries in Azure West Europe slowed and timed out as storage pods fell behind and kept restartingInfluxData · 2026same root cause · shared Database
IL-0435Error rates rose as Aurora MySQL killed connections and declined queries to avoid OOM while load metrics stayed flatCyberAgent · 2026same root cause · shared Database
IL-0497Buttondown's database ran out of connections twice in one day and requests failed while health checks mostly passedButtondown · 2026same root cause · shared Database
IL-0288ZooKeeperWait rose to thousands of seconds on three redundant ClickHouse instances, degrading a CDN77 data pipelineCDN77 · 2026same root cause · shared Database
IL-0350Hosts in an IONOS TXL cluster lost connectivity when an InfiniBand fabric resweep failed on a full multicast tableIONOS Cloud · 2026same root cause · shared Database
IL-0305Replicas of one Intercom Vitess shard hit 100% CPU and fell up to 2.2 hours behind, serving stale inbox dataIntercom · 2026same root cause · shared Database
IL-0390PostHog US Cloud event ingestion slowed to delays of up to 2 days as writes to the Persons Postgres table stalledPostHog · 2025same root cause · shared Database
IL-0100PostHog's feature flags pods were packed onto Kubernetes nodes that were too small for their CPU requests, and CPU saturation above 90% caused three outages in ten days through Redis overload, connection pool exhaustion and slow queriesPostHog · 2025same root cause · shared Database
IL-0287One overloaded shard of MongoDB's internal monitoring database delayed Atlas metrics, alerts and cluster operationsMongoDB · 2025same root cause · shared Database
IL-0557Database transaction locks piled up on Storj's US1 satellite, and uploads and downloads failed with timeouts for 2 hoursStorj · 2025same root cause · shared Database
IL-0551Bitbucket Cloud's overloaded primary database failed over, and the website, API and Pipelines were slow for almost a dayAtlassian · 2025same root cause · shared Database
IL-0298Wikimedia edits failed for 38 minutes when sessionstore Cassandra nodes in both data centres crashed on full disksWikimedia Foundation · 2025same root cause · shared Database
IL-0312Gadget's main Postgres did not start again after a restart to raise max_connections, and the platform went downGadget · 2024same root cause · shared Database
IL-0544Wasabi's database cache stopped responding when its queueing service filled up, and S3 failed in all regionsWasabi · 2024same root cause · shared Database
IL-0447An every RDS for MySQL instance slowed badly when its gp2 EBS BurstBalance ran out and IOPS fell to the baselineevery · 2024same root cause · shared Database
IL-0375MongoDB Atlas cluster changes and alerts lagged for hours after a control plane metadata migration congested a databaseMongoDB · 2024same root cause · shared Database
IL-0110A Grafana Agent pod's high memory use and crash-looping Hangfire pods drove a Kubernetes node into system OOM and NotReady, twice in one dayDFDS · 2024same root cause · shared Database
IL-0550Bitbucket Cloud's database slowed until connection pools saturated and requests timed out, leaving Pipelines pendingAtlassian · 2024same root cause · shared Database
IL-0270Discord's ScyllaDB authentication cluster overloaded during an OS upgrade, and logins failed for about 50 minutesDiscord · 2023same root cause · shared Database
IL-0202A burst of queries and database writes exhausted connection pools and memory on Honeycomb's ingest hosts, and Kubernetes crash-loop back-off kept failed hosts offline so ingest capacity stayed too low to recoverHoneycomb · 2023 · sev1same root cause · shared Database
IL-0386After a move to Google Cloud, Postgres connection timeouts and memcached i/o timeouts spiked on GKE nodesincident.io · 2023same root cause · shared Database
IL-0326A retention clean-up job filled the disk of MailPace's managed Postgres, which stayed offline for just over two hoursMailPace · 2023same root cause · shared Database
IL-0546Buildkite jobs could not go to newly connected agents once agent IDs passed a 32-bit integer foreign key's limitBuildkite · 2023same root cause · shared Database
IL-0453Hakuna API latency spiked every day during the ElastiCache Redis backup as memory filled and the backup went forklessHyperconnect · 2022same root cause · shared Database backups and snapshots
IL-0500UToronto JupyterHub logins and server starts returned 500 errors when the hub's sqlite database disk filled up2i2c · 2022same root cause · shared Database
IL-0301Basecamp 3's primary database went into total gridlock at the top of the hour and Basecamp 3 went down twice37signals · 2022same root cause · shared Database
IL-0206Consul agents in GitLab.com's GKE pods were repeatedly OOM-killed, so the Rails pods lost database replica discovery and sent every query to the primaryGitLab · 2022same root cause · shared Database
IL-0302Peak load on GitHub's mysql1 MySQL cluster maxed out its database proxy's connections and stopped writes in March 2022GitHub · 2022same root cause · shared Database
IL-0212Many Slack users could not connect because a Vitess keyspace for channel membership was overloaded by cache-miss queriesSlack · 2022same root cause · shared Database
IL-0456Inflearn went down six times during a January 2022 free-course event as slow queries piled up on Aurora PostgreSQLInflab · 2022same root cause · shared Database
IL-0321GCP snapshots on all Patroni nodes stalled GitLab.com's primary PostgreSQL disk, Patroni failed over and 5xx spikedGitLab · 2021same root cause · shared Database
IL-0496Ably's Cassandra hit 100% CPU in every region and queries timed out globally, and the load returned on two more eveningsAbly · 2020same root cause · shared Database
IL-0443A Repro Aurora MySQL reader restarted unexpectedly and writer insert latency rose about sevenfold for a day or moreRepro · 2019same root cause · shared Database
IL-0037Image registry rate-limited a whole region after a crash-looping DaemonSet with imagePullPolicy Always pulled through three NAT instancesDatadog · 2019same root cause · shared Database
IL-0297Mezmo users could not sign in and log indexing lagged after the auth cache's Redis servers were OOM killedMezmo · 2019same root cause · shared Database
IL-0211A Mandrill PostgreSQL shard shut down at transaction ID wraparound and email sending was impaired for about 40 hoursMailchimp · 2019same root cause · shared Database
IL-0064CPU-heavy pods packed onto one Google Cloud node drove it to kernel panics, and the crash moved from node to node until the site was downMoonlight · 2019same root cause · shared Database
IL-0300Basecamp 3 went read-only for almost five hours when its events table reached the ceiling of 2,147,483,64737signals · 2018same root cause · shared Database
IL-0333A downsized RDS PostgreSQL database maxed out its CPU at US peak and failing ELB health checks took buildkite.com downBuildkite · 2016same root cause · shared Database
IL-0282DynamoDB in US-East reached about 55% request errors as storage servers overloaded its metadata serviceAmazon Web Services · 2015same root cause · shared Database
IL-0383PagerDuty's shared Cassandra cluster degraded during a repair, delaying notifications and losing incoming eventsPagerDuty · 2014 · sev1same root cause · shared Database
IL-0320Postmark's primary MySQL disk filled but MySQL kept running, so MySQL-MMM never failed over and sending was delayedPostmark · 2011same root cause · shared Database
Check your cluster for this
For AI tools and scripts
- This case as JSON: https://incidentlib-api.benchlet.com/cases/IL-0309
- The cases most like it: https://incidentlib-api.benchlet.com/cases/IL-0309/similar
- MCP server (Streamable HTTP, no key):
https://incidentlib-mcp.benchlet.com/mcp
The API needs no key. The MCP server offers search_incidents, get_incident, list_incidents, get_topic and vocab; both are explained on API and MCP.