Technical notes organized by domain - architecture decisions, debugging stories, experiments, and lessons from production.https://islomcodes.uz/en-ushttps://islomcodes.uz/articles/idempotency-keys/https://islomcodes.uz/articles/idempotency-keys/How we eliminated duplicate charges and side effects using idempotency keys — design, implementation, and the edge cases that almost broke production.Sat, 15 Nov 2025 00:00:00 GMTapi-designreliabilitypatterns.NETRedisPostgreSQLhttps://islomcodes.uz/articles/circuit-breaker-downstream/https://islomcodes.uz/articles/circuit-breaker-downstream/Polly integration, failure thresholds, and the half-open state that prevented a cascade outage.Wed, 08 Oct 2025 00:00:00 GMTresiliencecircuit-breakerpolly.NETRedishttps://islomcodes.uz/articles/zero-downtime-deployments/https://islomcodes.uz/articles/zero-downtime-deployments/Rolling updates aren't enough when you have long-lived connections. Notes from implementing blue-green deployments with connection draining.Thu, 02 Oct 2025 00:00:00 GMTdeploymentskubernetesreliabilityKubernetesDockerNginxhttps://islomcodes.uz/articles/minimal-api-performance/https://islomcodes.uz/articles/minimal-api-performance/Benchmarking .NET Minimal APIs with source-generated JSON serialization — 3x throughput improvement with less allocation.Thu, 18 Sep 2025 00:00:00 GMTperformancedotnetbenchmarks.NETC#https://islomcodes.uz/articles/missing-index-explain/https://islomcodes.uz/articles/missing-index-explain/A 4-second query that looked innocent in staging — sequential scan on 40M rows in production.Fri, 05 Sep 2025 00:00:00 GMTpostgresqlindexesquery-planningPostgreSQLhttps://islomcodes.uz/articles/hpa-custom-metrics/https://islomcodes.uz/articles/hpa-custom-metrics/CPU-based HPA failed us during traffic spikes. Switching to request-rate metrics from Prometheus fixed autoscaling lag.Fri, 22 Aug 2025 00:00:00 GMTautoscalingobservabilitykubernetesKubernetesPrometheushttps://islomcodes.uz/articles/graceful-shutdown/https://islomcodes.uz/articles/graceful-shutdown/SIGTERM handling, draining in-flight requests, and the 30-second window Kubernetes gives you.Fri, 01 Aug 2025 00:00:00 GMTreliabilityaspnetcorekubernetes.NETKuberneteshttps://islomcodes.uz/articles/saga-order-fulfillment/https://islomcodes.uz/articles/saga-order-fulfillment/Choreography vs orchestration — why we picked orchestrated sagas with compensating transactions.Fri, 25 Jul 2025 00:00:00 GMTsagadistributed-transactionsorders.NETPostgreSQLRedishttps://islomcodes.uz/articles/connection-pooling/https://islomcodes.uz/articles/connection-pooling/PgBouncer vs built-in pooling — benchmarks, configuration, and why we run both in production.Thu, 10 Jul 2025 00:00:00 GMTdatabasepoolingperformancePostgreSQLDockerhttps://islomcodes.uz/articles/api-key-rotation/https://islomcodes.uz/articles/api-key-rotation/Dual-key validation window, gradual client migration, and the revocation list we keep in Redis.Thu, 12 Jun 2025 00:00:00 GMTsecurityapi-keysrotationRedis.NEThttps://islomcodes.uz/articles/cache-stampede/https://islomcodes.uz/articles/cache-stampede/Hot key expiration caused a thundering herd that took down Redis and cascaded to PostgreSQL. Postmortem and fix.Thu, 05 Jun 2025 00:00:00 GMTcachingincidentredisRedis.NETPostgreSQLhttps://islomcodes.uz/articles/event-sourcing-notes/https://islomcodes.uz/articles/event-sourcing-notes/Six months with event sourcing on an order management system — audit trail wins, operational complexity costs.Tue, 20 May 2025 00:00:00 GMTevent-sourcingarchitecturecqrsPostgreSQL.NEThttps://islomcodes.uz/articles/channel-background-workers/https://islomcodes.uz/articles/channel-background-workers/Replacing Task.Run fire-and-forget with System.Threading.Channels — backpressure, clean shutdown, metrics.Wed, 14 May 2025 00:00:00 GMTchannelsbackground-servicesconcurrency.NETC#https://islomcodes.uz/articles/profiling-dotnet/https://islomcodes.uz/articles/profiling-dotnet/dotnet-trace, EventPipe, and continuous profiling with minimal overhead — our observability stack for latency investigation.Sat, 12 Apr 2025 00:00:00 GMTprofilingobservabilitydotnet.NETLinuxhttps://islomcodes.uz/articles/multi-stage-dotnet-images/https://islomcodes.uz/articles/multi-stage-dotnet-images/Cutting image size from 1.2 GB to 210 MB and why chiseled images matter for pull time on Kubernetes.Tue, 08 Apr 2025 00:00:00 GMTdockerdotnetimagesDocker.NEThttps://islomcodes.uz/articles/iam-ci-least-privilege/https://islomcodes.uz/articles/iam-ci-least-privilege/Scoped OIDC roles for GitHub Actions — no long-lived AWS keys in repository secrets.Wed, 02 Apr 2025 00:00:00 GMTsecurityawsiamci-cdAWSGitHub Actionshttps://islomcodes.uz/articles/tls-termination-patterns/https://islomcodes.uz/articles/tls-termination-patterns/Three patterns we evaluated for mTLS between services — latency, ops burden, and cert rotation.Sat, 22 Mar 2025 00:00:00 GMTtlsmTLSarchitectureKubernetesNginxhttps://islomcodes.uz/articles/rate-limiting-design/https://islomcodes.uz/articles/rate-limiting-design/Token bucket vs sliding window vs fixed window — benchmarks and the hybrid approach we shipped.Sat, 01 Mar 2025 00:00:00 GMTrate-limitinggatewayapiRedis.NETKuberneteshttps://islomcodes.uz/articles/resource-limits-rightsizing/https://islomcodes.uz/articles/resource-limits-rightsizing/Limits too low cause OOMKill loops. Too high waste money. How we right-sized from production metrics.Fri, 28 Feb 2025 00:00:00 GMTkubernetesresourceslimitsKuberneteshttps://islomcodes.uz/articles/payment-gateway-capacity/https://islomcodes.uz/articles/payment-gateway-capacity/Back-of-envelope math for throughput, connection pools, and the assumptions that broke during Black Friday.Fri, 14 Feb 2025 00:00:00 GMTcapacity-planninggatewaytrade-offsKubernetesPostgreSQLRedishttps://islomcodes.uz/articles/github-actions-deploy-pipeline/https://islomcodes.uz/articles/github-actions-deploy-pipeline/Build, test, and deploy — the workflow we use for this journal and our internal docs.Fri, 10 Jan 2025 00:00:00 GMTci-cdgithub-actionsautomationGitHub ActionsDockerhttps://islomcodes.uz/articles/debugging-syscall-latency/https://islomcodes.uz/articles/debugging-syscall-latency/P99 latency spiked but CPU was idle — tracing syscalls found we were blocked on fsync, not compute.Thu, 05 Dec 2024 00:00:00 GMTlinuxdebuggingperformanceLinuxPostgreSQLhttps://islomcodes.uz/articles/compose-local-stack/https://islomcodes.uz/articles/compose-local-stack/Postgres, Redis, Kafka, and the gateway — one command for new engineers to get a working environment.Fri, 22 Nov 2024 00:00:00 GMTdocker-composelocal-devdxDockerPostgreSQLRedishttps://islomcodes.uz/articles/dns-failover-incident/https://islomcodes.uz/articles/dns-failover-incident/TTL misconfiguration routed 40% of traffic to a decommissioned region for 18 minutes.Thu, 17 Oct 2024 00:00:00 GMTdnsincidentfailoverAWSLinuxhttps://islomcodes.uz/articles/read-heavy-vs-write-heavy/https://islomcodes.uz/articles/read-heavy-vs-write-heavy/Questions I ask before choosing caching, replication, or sharding — a reusable checklist from five system designs.Tue, 03 Sep 2024 00:00:00 GMTtrade-offschecklistdesignPostgreSQLRedishttps://islomcodes.uz/articles/jwt-vs-session-tokens/https://islomcodes.uz/articles/jwt-vs-session-tokens/Why we use opaque session tokens at the gateway and JWT only for service-to-service calls.Wed, 14 Aug 2024 00:00:00 GMTsecurityauthjwt.NETRedishttps://islomcodes.uz/articles/structured-logging-migration/https://islomcodes.uz/articles/structured-logging-migration/Six services, three log formats, one observability stack — how we standardized on Serilog + OpenTelemetry.Thu, 18 Jul 2024 00:00:00 GMTobservabilityloggingmigration.NETKuberneteshttps://islomcodes.uz/articles/spot-instance-experiment/https://islomcodes.uz/articles/spot-instance-experiment/40% cost reduction on batch jobs — interruption handling, checkpointing, and what we never run on spot.Thu, 20 Jun 2024 00:00:00 GMTcostawsspotAWSKuberneteshttps://islomcodes.uz/articles/file-descriptor-limits/https://islomcodes.uz/articles/file-descriptor-limits/Too many open sockets crashed the gateway with 'too many open files' — ulimits, kernel tuning, and Kubernetes limits.Thu, 30 May 2024 00:00:00 GMTlinuxnetworkinglimitsLinuxKuberneteshttps://islomcodes.uz/articles/distributed-locks-redlock/https://islomcodes.uz/articles/distributed-locks-redlock/When single-instance Redis locks fail, Redlock trade-offs, and why we still prefer database advisory locks for money.Fri, 12 Apr 2024 00:00:00 GMTredislockingdistributed-systemsRedis.NEThttps://islomcodes.uz/articles/k6-load-test-baseline/https://islomcodes.uz/articles/k6-load-test-baseline/Smoke, load, stress, and soak scenarios — the four scripts we run before every major release.Fri, 15 Mar 2024 00:00:00 GMTload-testingk6benchmarksGoKubernetes