Topic: kubernetes
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Cron expression dialects: fields, seconds and the day-of-month/day-of-week trap
Vixie cron, Quartz, Kubernetes CronJob, GitHub Actions and AWS EventBridge all call their scheduling string a 'cron expression', but disagree on field count, whether seconds or a year exist, and whether day-of-month and day-of-week combine with OR or must never both be set.
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Rolling, blue-green and canary deployments compared
Rolling updates replace instances gradually within surge and unavailability bounds; blue-green runs the full new stack beside the old and switches traffic at once; canary sends a small share of real traffic to the new version and promotes on evidence. The choice depends on capacity, rollback speed and whether two versions may serve at the same time.
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ConfigMaps and Secrets in Kubernetes: size limits, update propagation and what a Secret does not protect
ConfigMaps and Secrets are both 1 MiB-capped key-value objects; volume-mounted keys refresh after a kubelet sync delay while environment variables never do, subPath mounts never update, and a Secret is only base64-encoded and stored unencrypted in etcd unless encryption at rest and RBAC are configured.
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After ingress-nginx retirement: validating a parallel Gateway API migration
Ingress NGINX maintenance ended in March 2026. Use the official migration tooling to draft Gateway API resources, identify unsupported behaviour, and validate a separate traffic path before switching production traffic.
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Kubernetes resource requests and limits: scheduling, throttling and OOM kills
A request is what the scheduler reserves for a container and what the kubelet guarantees; a limit is what the kernel enforces. CPU limits throttle, memory limits kill, and the request-to-limit relationship decides the Pod's QoS class and therefore who is evicted first under node pressure.
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Rollout strategies: rolling, blue-green and canary
A rolling rollout replaces instances step by step within the limits of maxSurge and maxUnavailable; blue-green runs the new stack in full alongside the old one and switches traffic all at once; canary sends a small share of real requests to the new version and raises it based on metrics. The choice depends on spare capacity, the desired rollback time, and whether two versions may run at the same time.
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