Why I replaced an eight-second confirmation request with an asynchronous intent
A write-path redesign that released Tomcat request threads immediately and fixed an overly broad rule that could supersede unrelated pending approval actions.
Backend
API, domain modeling, authentication, consistency, and server-side engineering.
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What should a rate limiter count when one API call fans out six times?
A redesign of a limiter that returned 429 during a normal seat search because its unit did not match the actual upstream call graph.
Replacing a broken Set-Cookie proxy with a one-time SSO code exchange
How multiple Set-Cookie headers exposed a fragile proxy boundary and led to a 256-bit, atomically consumed Redis authorization-code protocol.
Reducing 100 same-seat requests to one upstream write
A durable reservation queue using Postgres intents, short claim leases, an outbox, and seat-level coordination around a non-idempotent school API.
Redrawing the failure boundary to preserve 70 successful LMS files
How four unsupported attachments led to explicit origin checks and a partial-success policy instead of discarding an otherwise valid export.
Why a 3/3 connection indicator still left private tools unavailable
A three-service authentication incident resolved by separating web identity, provider credentials, and MCP session grants.
Why the survival score has a SQL layer and a Java layer
PostGIS derives facts while a pure policy function handles weights and missing data, making a composite score explainable and testable.
Aligning identity boundaries from the browser to private MCP tools
How discarding client-claimed principals and separating a server-verified subject from an explicit MCP session prevents IDOR on principal-owned threads and silent privilege downgrade.