Archives

A source-disciplined design for a multi-AZ, queue-backed order-processing system, including its failure boundaries and delivery guarantees.

A source-backed analysis of Discord's message-storage evolution, Cassandra data modeling, and a clearly separated ScyllaDB migration design.

A source-disciplined system-design analysis of immutable blobs, erasure coding, tiered storage, and durability at exabyte scale.

A source-disciplined system-design analysis of external consistency, time uncertainty, Paxos-style replication, sharding, and multi-region operation.

A source-disciplined system-design analysis of tail latency, variance, hedged requests, tied requests, and request amplification.

A source-backed guide to monitoring latency, traffic, errors, saturation, and turning SLO evidence into actionable alerts.

A source-backed system-design treatment of transactions, recovery, load shedding, and client-side throttling.

A source-backed system-design analysis of the latency, routing, privacy, and operational boundaries behind a global consumer DNS resolver.

A source-backed analysis of idempotency keys, safe retries, concurrency, replay, and a proposed payment API design.

A source-backed analysis of dual-write migrations, backfill, shadow reads, cutover, and correctness under continuous production traffic.

How FinPay reasons about correlating Prometheus alerts and OpenTelemetry traces without allowing an LLM to become an operational or money-moving authority.

A problem-driven design for keeping probabilistic AI signals out of authoritative payment decisions while preserving safety, latency, replayability, and auditability.

A practical design for shared LLM integration with BYOK credentials, resilience controls, idempotency, and auditable outcomes.

A problem-driven design for turning an OpenTelemetry traceId into a bounded, auditable incident summary without giving an LLM authority over financial actions.

A guarded design for scoring ledger events asynchronously without putting AI on the money path.

A practical design for extracting KYC fields from identity documents, validating them with deterministic rules, and routing uncertain cases to human review.

A practical design for using an LLM to write notification copy without letting it change payment facts, block delivery, or leak credentials.

A practical design for explaining customer transactions with retrieval-augmented generation over ledger and transfer events.

An operational design for timezone-aware cron, one-off jobs, and DAG workflows with at-least-once execution and auditable recovery.

An operational design for durable, idempotent, multi-channel notifications at one million channel messages per day.

A practical design for a read-heavy, ranked news feed that balances freshness, predictable pagination, and fan-out cost.

A practical design for low-latency request limits, burst handling, route policies, and explicit failure behavior.

A strongly consistent design for charges, refunds, payouts, disputes, and auditable money movement.

A practical design for durable, versioned object storage with multipart transfer, tenant-local deduplication, temporary sharing, metadata search, and CDN delivery.

A scoped design for ordered, multi-device chat with durable history and large-scale concurrent connections.

A practical design for low-latency, personalized, typo-tolerant search suggestions at high QPS.

A practical design for durable URL mappings, low-latency redirects, custom aliases, expiry, and asynchronous analytics.

A production-oriented design for ingesting, transcoding, packaging, protecting, and delivering video with predictable latency and cost.

A problem-first guide to using OOP, SOLID, and common design patterns in Java without adding abstraction that the code does not need.

A practical framework for answering senior behavioral questions with clear trade-offs, evidence, uncertainty, and ownership.

A practical Spring Boot interview guide covering IoC and DI, bean scopes, configuration, web annotations, and the transaction proxy pitfalls that cause production bugs.

A practical system-design interview guide covering requirements, capacity, data, failure handling, scalability, and observability.

A practical Kafka interview guide covering topics, partitions, delivery semantics, ordering, consumer groups, offsets, serialization, and metadata.

A practical database and SQL interview guide covering joins, constraints, transactions, aggregation, SQL injection, and the trade-offs behind common schema and query decisions.

A practical interview guide to microservice boundaries, communication, resilience, and distributed transactions in Spring.

A practical set of 50 Java interview questions covering OOP foundations, SOLID trade-offs, composition, interface design, and senior-level refactoring decisions.

A practical Java Core interview guide covering JVM memory, garbage collection, the Java Memory Model, and concurrency, from foundational questions to production trade-offs.

A production-oriented guide to Java concurrency: shared state, thread pools, backpressure, CPU and I/O-bound work, and what Virtual Threads change.

A practical explanation of why Java remains widely used for backend systems, enterprise software, and long-lived engineering teams.

A practical guide to reducing load across the frontend, cache, database, backend, request path, monitoring, and autoscaling layers.

A practical comparison of Tomcat, Jetty, and Undertow, covering request handling, embedding, protocol support, and application fit.

A practical explanation of Project Loom, virtual threads, their trade-offs, and when they fit Java applications.

A practical overview of GraalVM, Native Image, polyglot execution, and the trade-offs against a standard JVM deployment.