Technical blog

BitPage

A technical engineer's blog: real problems, real fixes, real numbers. Backend, databases, infra, incident post-mortems, security, AI-native workflows.

8 articles

7 tracks

36 tags

Recent

10.10.2026 Mobile

Room 3 froze on a suspending @Transaction: the SQLite driver you pass picks your connection pool

Room 3 reads hasConnectionPool off the driver you hand setDriver(). AndroidSQLiteDriver returns true, so Room installs a passthrough pool holding exactly one thread-confined connection, and a suspending @Transaction can block there with no crash, no ANR and nothing in logcat. BundledSQLiteDriver returns false, so Room runs its own pool of four readers and one writer, and resets PRAGMA synchronous on every connection it opens.

26.09.2026 Backend

How to never pay a generative API twice: a durable task table, not a retrying job queue

The instant you might have been charged is not the provider's response, it is the moment before the request leaves your process. Write it to a row before the HTTP call and a dead worker becomes recoverable without guessing: nothing written means retry is safe, a saved request id means poll, and the gap between them needs a third terminal state.

21.09.2026 Security

curl error 60: the message text fingerprints the TLS backend, not your certificate

The same untrusted root produces six different sentences depending on which TLS library curl was linked against, and on wolfSSL it is not even error 60 but 77. Read the wording as a build identifier, run curl -V first, and only then go looking at the trust store.

16.09.2026 Databases

PostgreSQL index bloat: why VACUUM never shrinks an index, and how to measure it with avg_leaf_density

A b-tree that has lost most of its keys keeps every page it allocated: PostgreSQL reclaims completely empty index pages, but a page with a few keys left on it stays put, and no autovacuum setting changes that. Measure the damage with pgstatindex.avg_leaf_density against the b-tree default fillfactor of 90, predict the recovery as size x density / 90, and fix it with REINDEX rather than VACUUM FULL.

06.09.2026 Incidents

Mass segfaults on a ZFS host: not bad RAM, an unsigned underflow in zfs_fillpage()

A host that answers on no port while the kernel keeps logging is not failing memory. In OpenZFS before 2.4.4 and 2.3.9, zfs_fillpage() computes io_len = i_size - io_off in unsigned types: race an mmap read against an in-place truncate and the length underflows, so dmu_read() zero-fills physical memory far past the page. Fixed on 21 August 2026 in 2.4.4 and 2.3.9 — but not in 2.2.11, released the same minute.

06.08.2026 Databases

PostgreSQL conflict with recovery: why both standard fixes make it worse under Patroni

With replication slots enabled, hot_standby_feedback moves the bloat risk onto the primary; raising max_standby_streaming_delay feeds the HAProxy check that ejects the replica. Two hundred cancelled queries and thirty-odd replica ejections looked like one problem, but barely one in twenty lined up.

Tracks

Backend

PHP, Laravel, GraphQL, domain modeling, server-side architecture. Notes from mature monoliths and greenfields.

Latest: How to never pay a generative API twice: a durable task table, not a retrying job queue

Databases

PostgreSQL, ClickHouse, MySQL. Migrations, optimization under load, incident post-mortems, escaping rules, common traps in mixed stacks.

Latest: PostgreSQL index bloat: why VACUUM never shrinks an index, and how to measure it with avg_leaf_density

Infrastructure

Ansible, Terraform, Proxmox, libvirt/KVM, Docker, LXC, edge proxies, network, DNS. Bare metal, no clouds.

Latest: How to migrate a stateful Docker app off a server with a dying disk

Incidents

Post-mortems with the full diagnosis: hypotheses, ruled-out theories, root cause, real numbers. How systems actually break.

Latest: Mass segfaults on a ZFS host: not bad RAM, an unsigned underflow in zfs_fillpage()

Security

CrowdSec, SSH, TLS, secrets, hardening. Replacing ritual defense with something you can actually verify.

Latest: curl error 60: the message text fingerprints the TLS backend, not your certificate

AI-native

Claude Code, MCP, agent memory, skill conventions, workflows. Building software with an AI partner, as a process.

Mobile

iOS and SwiftUI, Android and Kotlin, Apollo GraphQL. Live client-server integrations, on-device storage, server-driven UI, debugging the network layer.

Latest: Room 3 froze on a suspending @Transaction: the SQLite driver you pass picks your connection pool