https://ovini.site/blog/en/ Long-form posts on Rails internals, PostgreSQL at scale, distributed systems, and AI-assisted engineering. en Thu, 13 Aug 2026 12:00:00 GMT https://ovini.site/blog/en/how-a-coding-agent-operates-on-a-repository.html https://ovini.site/blog/en/how-a-coding-agent-operates-on-a-repository.html Thu, 13 Aug 2026 12:00:00 GMT Vinicius Pereira ai Not autocomplete, not magic: a loop of read, plan, edit, verify, running against a real filesystem. Traced against an actual change made to this site, including the part it got wrong. https://ovini.site/blog/en/hotwire-native-webview-bridge.html https://ovini.site/blog/en/hotwire-native-webview-bridge.html Thu, 06 Aug 2026 12:00:00 GMT Vinicius Pereira hotwire Hotwire Native is not a wrapper around a website. It is a native app that delegates screens, and the moment you understand who owns the back stack, half the confusion disappears. https://ovini.site/blog/en/connection-pooling-why-your-database-runs-out-of-connections.html https://ovini.site/blog/en/connection-pooling-why-your-database-runs-out-of-connections.html Thu, 21 May 2026 12:00:00 GMT Vinicius Pereira postgres Rails opens one connection per thread, Postgres charges ~10MB per connection, and nobody notices until concurrency spikes. PgBouncer, pool sizing, and the math that actually matters. https://ovini.site/blog/en/you-don-t-understand-machine-learning-until-you-implement-it-from-scratch.html https://ovini.site/blog/en/you-don-t-understand-machine-learning-until-you-implement-it-from-scratch.html Thu, 14 May 2026 12:00:00 GMT Vinicius Pereira ml Calling sklearn.fit() isn't understanding. Building a perceptron, logistic regression and a net that solves XOR in Ruby is. ML is algebra and optimization — not magic. https://ovini.site/blog/en/gradient-descent-visually-explained.html https://ovini.site/blog/en/gradient-descent-visually-explained.html Thu, 07 May 2026 12:00:00 GMT Vinicius Pereira ml Cost function is a surface. Derivative is slope. θ = θ − α·∇J(θ). Every neural net you've ever heard of is this rule, repeated. https://ovini.site/blog/en/epoll-and-io-uring-explained-visually.html https://ovini.site/blog/en/epoll-and-io-uring-explained-visually.html Thu, 30 Apr 2026 12:00:00 GMT Vinicius Pereira infra Blocking IO → select → poll → epoll → io_uring. Every step exists because the previous one stalled. Async isn't a language feature, it's a kernel feature. https://ovini.site/blog/en/how-the-linux-kernel-actually-receives-an-http-request.html https://ovini.site/blog/en/how-the-linux-kernel-actually-receives-an-http-request.html Thu, 23 Apr 2026 12:00:00 GMT Vinicius Pereira infra NIC → driver → IRQ → softirq → IP → TCP → socket buffer → accept queue → Puma. Your framework is the last 5% of the request. The rest is kernel. https://ovini.site/blog/en/the-exactly-once-myth.html https://ovini.site/blog/en/the-exactly-once-myth.html Thu, 16 Apr 2026 12:00:00 GMT Vinicius Pereira distributed Exactly-once doesn't exist on the network. What exists is at-least-once plus idempotency. Stop chasing a marketing myth — design for reality and sleep at night. https://ovini.site/blog/en/how-to-avoid-retry-storms-in-background-jobs.html https://ovini.site/blog/en/how-to-avoid-retry-storms-in-background-jobs.html Thu, 09 Apr 2026 12:00:00 GMT Vinicius Pereira distributed External API goes down. 100k Sidekiq jobs decide to retry at the same time. Jitter, circuit breaker, DLQ — retry isn't a fix, it's a deferral strategy. https://ovini.site/blog/en/idempotency-in-real-systems.html https://ovini.site/blog/en/idempotency-in-real-systems.html Thu, 02 Apr 2026 12:00:00 GMT Vinicius Pereira distributed At-least-once is reality. A unique constraint is the only real guarantee. Idempotency-Key, dedupe tables — survival in distributed systems. https://ovini.site/blog/en/lock-contention-the-silent-killer-in-postgresql.html https://ovini.site/blog/en/lock-contention-the-silent-killer-in-postgresql.html Thu, 26 Mar 2026 12:00:00 GMT Vinicius Pereira postgres A 10ms migration that freezes production for 40 minutes. ALTER TABLE grabbing ACCESS EXCLUSIVE. pg_locks + pg_stat_activity. Locks are invisible — until they aren't. https://ovini.site/blog/en/what-vacuum-actually-does-in-postgresql.html https://ovini.site/blog/en/what-vacuum-actually-does-in-postgresql.html Thu, 19 Mar 2026 12:00:00 GMT Vinicius Pereira postgres MVCC, dead tuples, bloat, autovacuum, transaction wraparound. VACUUM isn't cleanup — it's how Postgres works. Ignoring it is how you wake up at 3am. https://ovini.site/blog/en/explain-analyze-should-be-mandatory.html https://ovini.site/blog/en/explain-analyze-should-be-mandatory.html Thu, 12 Mar 2026 12:00:00 GMT Vinicius Pereira postgres Junior runs the query. Senior runs the query plan. Seq Scan, Index Scan, Bitmap Heap, estimated vs actual, BUFFERS — reading the plan isn't optional, it's the job. https://ovini.site/blog/en/you-don-t-understand-rails-until-you-understand-the-full-request-cycle.html https://ovini.site/blog/en/you-don-t-understand-rails-until-you-understand-the-full-request-cycle.html Thu, 05 Mar 2026 12:00:00 GMT Vinicius Pereira rails Rails isn't magic. Rails is Rack, TCP, threads, middleware, SQL and Ruby objects on the heap. Understand what happens before and after your controller. https://ovini.site/blog/en/refactoring-a-monolith-without-blowing-up-production.html https://ovini.site/blog/en/refactoring-a-monolith-without-blowing-up-production.html Thu, 26 Feb 2026 12:00:00 GMT Vinicius Pereira architecture Microservices aren't the answer. Refactoring a monolith is an art — strangler fig, feature flags, stepwise schema migration. What nobody tells you about the process. https://ovini.site/blog/en/how-to-identify-a-performance-bottleneck-in-minutes.html https://ovini.site/blog/en/how-to-identify-a-performance-bottleneck-in-minutes.html Thu, 19 Feb 2026 12:00:00 GMT Vinicius Pereira performance Every slow app has ONE dominant bottleneck. Guessing doesn't cut it. Learn the suspect hierarchy, the right tools and the workflow that goes straight to the cause. https://ovini.site/blog/en/debugging-memory-leaks-in-ruby-without-crying.html https://ovini.site/blog/en/debugging-memory-leaks-in-ruby-without-crying.html Thu, 12 Feb 2026 12:00:00 GMT Vinicius Pereira performance Ruby has a GC. So classic leaks don't really exist. What does exist is bloat — and knowing the difference is what separates senior from junior here. https://ovini.site/blog/en/writing-a-simple-dsl-from-scratch-in-ruby.html https://ovini.site/blog/en/writing-a-simple-dsl-from-scratch-in-ruby.html Thu, 05 Feb 2026 12:00:00 GMT Vinicius Pereira ruby Rails, RSpec, Sidekiq, Devise — every famous gem is a DSL. And none of them is magic. They're simple metaprogramming tricks you can replicate in an afternoon. https://ovini.site/blog/en/how-activerecord-builds-sql-under-the-hood.html https://ovini.site/blog/en/how-activerecord-builds-sql-under-the-hood.html Thu, 29 Jan 2026 12:00:00 GMT Vinicius Pereira rails You're not building SQL. You're building a tree. Understand Arel, bind parameters, lazy evaluation and the real difference between includes, preload and eager_load. https://ovini.site/blog/en/ancestors-chain-how-ruby-actually-resolves-methods.html https://ovini.site/blog/en/ancestors-chain-how-ruby-actually-resolves-methods.html Thu, 22 Jan 2026 12:00:00 GMT Vinicius Pereira ruby The favorite interview question to separate a Rubyist from someone who just writes Ruby. Include, prepend, singleton classes — every doubt has the same answer. https://ovini.site/blog/en/how-ruby-resolves-methods-internally.html https://ovini.site/blog/en/how-ruby-resolves-methods-internally.html Thu, 15 Jan 2026 12:00:00 GMT Vinicius Pereira ruby When you call user.name, Ruby performs a ritual. Method lookup, inline cache, method_missing, singleton classes — the real mechanics behind a simple call. https://ovini.site/blog/en/gil-the-lock-every-rubyist-needs-to-understand.html https://ovini.site/blog/en/gil-the-lock-every-rubyist-needs-to-understand.html Thu, 08 Jan 2026 12:00:00 GMT Vinicius Pereira ruby Ruby has no real parallelism because of the GIL — a half-truth said with confidence. Understand the GVL for real, when threads help and when they become traps. https://ovini.site/blog/en/understanding-ruby-s-runtime-not-just-the-language.html https://ovini.site/blog/en/understanding-ruby-s-runtime-not-just-the-language.html Thu, 01 Jan 2026 12:00:00 GMT Vinicius Pereira ruby Most know the language. Almost none know the runtime. YARV, heap, GC, GVL, inline cache — where engineering lives and where production bugs are born.