Senior backend engineer and tech lead in Tokyo — distributed systems on AWS and GCP, Go and Java, and production LLM/RAG services.https://tagy.sd/https://tagy.sd/blog/recommendation-system-line-miniapp/https://tagy.sd/blog/recommendation-system-line-miniapp/The architecture behind a property-search platform delivered entirely through LINE — Go backend, LIFF mini-apps, an XGBoost inference service, and the batch pipelines that keep recommendations fresh.Sat, 22 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/production-serverless-aws-architecture/https://tagy.sd/blog/production-serverless-aws-architecture/Fifty-plus Lambda functions, hexagonal architecture, SQS-driven batch pipelines, and multi-region DR on AWS — the structure, queue design, and operational decisions behind an enterprise serverless platform.Sun, 26 Jul 2026 00:00:00 GMThttps://tagy.sd/blog/transactional-outbox-event-driven-microservices/https://tagy.sd/blog/transactional-outbox-event-driven-microservices/How we kept orders, payments, and downstream services consistent on Cloud Run and Spanner using the transactional outbox pattern and task-queue relay workers — and what we'd do differently.Sun, 14 Jun 2026 00:00:00 GMThttps://tagy.sd/blog/cloud-run-sidecar-auth/https://tagy.sd/blog/cloud-run-sidecar-auth/A sidecar proxy pattern on Cloud Run: ingress authentication, egress through a central internal API hub, and an internal load balancer doing the routing — mesh benefits without mesh weight.Sun, 12 Jul 2026 00:00:00 GMThttps://tagy.sd/blog/chat-thread-as-ui/https://tagy.sd/blog/chat-thread-as-ui/LIFF token verification, Flex Message carousels, rich menus, and chatbot flows as routing — chat-platform engineering as a backend discipline.Mon, 24 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/innodb-lock-contention/https://tagy.sd/blog/innodb-lock-contention/Up to a thousand concurrent Go workers, each upserting its own user's rows in MySQL — and InnoDB kept detecting deadlocks between them. The gap-lock mechanics, the fix menu ranked, and the deliberately boring choice.Sun, 30 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/multi-region-dr-terraform/https://tagy.sd/blog/multi-region-dr-terraform/Tokyo primary, Osaka standby, one Terraform module set: what to replicate, what to rehearse, and why an untested failover plan is a diagram, not a capability.Wed, 12 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/design-logs-like-an-api/https://tagy.sd/blog/design-logs-like-an-api/Business questions answered from CloudWatch Logs Insights: log-line contracts, why enriching an existing line beats adding a new one, JSON-escaping gotchas, and the retention trap.Wed, 26 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/push-notification-pipeline/https://tagy.sd/blog/push-notification-pipeline/Notification campaigns as scheduled batch jobs: eligibility and dedup pushed into the audience query, a send log that doubles as the resume checkpoint, throttling against platform quotas — and the two gates I'd add today.Fri, 28 Aug 2026 00:00:00 GMThttps://tagy.sd/blog/payment-gateway-abstraction/https://tagy.sd/blog/payment-gateway-abstraction/Card with 3DS, wallet, convenience store, and direct debit behind a single internal service — how a payment gateway abstraction keeps a provider's quirks out of your order flow.Sun, 28 Jun 2026 00:00:00 GMThttps://tagy.sd/blog/context-cancellation-postmortem/https://tagy.sd/blog/context-cancellation-postmortem/A production postmortem on Go context cancellation: a fire-and-forget cache write inherited the request's context and died with it — the diagnosis, the reverted first fix, and the boring final one.Sun, 19 Jul 2026 00:00:00 GMThttps://tagy.sd/blog/hexagonal-architecture-lambda/https://tagy.sd/blog/hexagonal-architecture-lambda/How fifty-plus TypeScript Lambda functions stayed testable and consistent: ten-line handlers, ports and adapters, and one use case serving API, queue, and batch entrypoints.Wed, 05 Aug 2026 00:00:00 GMT