The Software Engineering Podcast with Fexingo: Code, Architecture, and Engineering Best Practices

In this episode, Lucas and Luna dive into the story of a senior backend engineer at a mid-sized fintech company who systematically reduced database deadlocks by 95 percent. They break down the root cause—a combination of implicit table locks and poorly ordered transactions—and walk through the specific fix: introducing explicit row-level locking, reordering SQL statements to follow a consistent lo...

Episode 103 of The Software Engineering Podcast explores how one engineer built an AI-powered code review agent that automates 70 percent of repetitive comments, freeing senior developers for higher-level architectural decisions. Lucas and Luna discuss the practical implementation — using a fine-tuned LLM on a private codebase, integrating with GitHub's API, and handling false positives with a con...

In this episode, Lucas and Luna dive into the story of a serverless application that went haywire due to a hidden bug in a Lambda function's cold start logic. They explore how structured logging—with JSON-formatted logs and correlation IDs—allowed a single engineer to trace the issue across distributed systems in minutes. The episode covers the specific logging libraries and practices that turned...

In this episode, Lucas and Luna dive into a practical engineering story: how one engineer at a mid-size fintech company prevented a cascading failure by implementing circuit breakers between microservices. The discussion walks through the specific scenario—a downstream payment API latency spike that would have taken down the entire checkout flow—and how a simple Hystrix-style circuit breaker patte...

In this episode, Lucas and Luna dive into a real-world production outage caused by a single misconfigured database connection pool. They walk through how a popular e-commerce site went down for 45 minutes because of a connection pool set too low, spilling over into cascading failures across their microservices. They explain what connection pooling is, how to tune it, and the monitoring signals tha...

In this episode of The Software Engineering Podcast, Lucas and Luna dive into a bizarre production outage caused by a single Unicode character. They dissect how a zero-width space sneaked into a payment gateway's input validation, bypassing all regex checks and causing silent transaction failures. Lucas breaks down the technical specifics—how UTF-8 encoding works, why most sanitizers miss non-prin...

In Episode 98 of The Software Engineering Podcast, Lucas and Luna dive into a real-world incident where a single misconfigured DNS entry took down a multi-region e-commerce platform for 47 minutes. They walk through the architecture—how DNS resolution works, the difference between round-robin and geo-location routing, and the cascading failure that happened when a stale 'glue record' pointed to a...

Lucas and Luna dive into the story of how a single database index saved a startup's user-facing dashboard. When a page load hit 12 seconds during peak traffic, one engineer found the culprit: a full table scan on a 40-million-row table. The fix wasn't a $10,000 database upgrade or a caching layer — it was a composite index on three columns. Lucas walks through the query plan, the index structure,...

In this episode, Lucas and Luna dive into a specific engineer's battle against AWS Lambda cold starts. They break down how a serverless backend handling real-time analytics was suffering from three-second cold starts during traffic spikes, and how a combination of provisioned concurrency, VPC endpoint optimization, and a custom runtime in Rust cut latency by 60 percent. The discussion walks throug...

In this episode of The Software Engineering Podcast, Lucas and Luna dive into a 2025 incident where a seemingly harmless TypeScript type definition change cascaded into a three-hour production outage at a mid-size fintech company. They trace the root cause: an interface that was too permissive combined with a generic that silently widened the return type. The bug passed code review, passed CI, and...

Lucas and Luna dissect a real-world outage caused by a single misconfigured load balancer that took down a major e-commerce site for over an hour during a flash sale. They walk through the engineering details: how a health-check timeout setting caused the balancer to mark all backends as unhealthy, how the team debugged it, and what monitoring changes they made to prevent recurrence. Plus, they di...

In this episode, Lucas and Luna dissect a notorious production incident where a single null byte in a user input crashed a payment processing system handling thousands of transactions per minute. They trace the bug from a misconfigured web form to a C library's string handling, and explain how a tiny oversight in input sanitization cascaded into a full outage. Along the way, they discuss defensive...

In this episode, Lucas and Luna dissect a real-world incident where a poorly managed feature flag caused a cascading failure that took down a major e-commerce platform for over two hours. They walk through the chain of events: a developer enables a flag for internal testing, the flag's default value is 'true', a deployment script fails to reset it, and the new code path triggers a database bottlen...

Lucas and Luna dive into a real-world debugging story: a race condition in an order-processing system that caused duplicate shipments and lost revenue for a mid-size e-commerce company. They explore how the bug evaded testing, the specific timing window that triggered it, and the fix that prevented it from recurring. Along the way, they discuss concurrency gotchas in distributed systems, the limit...

In this episode, Lucas and Luna dive into a real-world case where a top-tier SaaS company cut its infrastructure bill by over half — not by migrating clouds or rewriting code, but by tuning a single PostgreSQL configuration parameter. They walk through the default settings that silently waste memory, the specific 'shared_buffers' and 'effective_cache_size' adjustments that turned the tide, and the...

In this episode, Lucas and Luna dissect a real-world software engineering disaster: a single poorly written regular expression that brought a major e-commerce site to its knees during Black Friday. They walk through how a catastrophic backtracking bug turned a harmless input validation check into a CPU-eating monster, triggering cascading failures across microservices. Learn what catastrophic back...

In this episode of The Software Engineering Podcast, Lucas and Luna dive into a real-world Kubernetes nightmare: a single misconfigured pod that silently caused cascading failures across a whole cluster. They walk through how an engineer at a mid-size fintech company discovered the root cause — not through monitoring alerts, but by noticing a subtle anomaly in request latency distributions. The fi...

Episode 87 of The Software Engineering Podcast digs into a real-world cost optimization story. Lucas and Luna walk through how a senior engineer at a mid-sized SaaS company slashed their AWS bill from $120,000 to $24,000 per month using a combination of Reserved Instances, Savings Plans, and right-sizing. They break down the math: 1-year vs 3-year commitments, partial upfront vs no upfront, and ho...

In episode 86 of The Software Engineering Podcast, Lucas and Luna explore how a senior engineer at a mid-sized SaaS company reduced continuous integration build times from 47 minutes to under 10. They break down the specific caching strategy — a combination of Docker layer caching, dependency pre-warming, and a custom GitHub Actions cache warmer — that eliminated redundant work across 150 develope...

In episode 85 of The Software Engineering Podcast, Lucas and Luna dive into a real-world production debugging story where flame graphs turned chaos into clarity. They walk through how a single engineer traced a mysterious CPU spike that was causing intermittent timeouts across a microservices architecture — and how a visual profiling tool cut the investigation from days to hours. Along the way, th...

In this episode of The Software Engineering Podcast with Fexingo, Lucas and Luna dive into a single tricky bug: a distributed lock implemented with Redis that caused intermittent failures in a high-traffic checkout system. They walk through the engineer's discovery of a missing atomicity guarantee in the lock acquisition path, the specific race window that allowed two processes to acquire the same...

Episode 83 of The Software Engineering Podcast with Fexingo: Lucas and Luna dive into the story of a software engineer at a fintech startup who noticed a suspicious log line during routine monitoring. That single log entry revealed an attacker had been exfiltrating customer data for weeks via a compromised API key. The engineer's quick detection and response prevented a full-blown data breach that...

In this episode, Lucas and Luna dive into the story of an engineer at a mid-size SaaS company who accidentally deployed a breaking change to production on a Friday afternoon. Instead of a panicked 20-minute scramble to revert via Git, she had already set up a one-line rollback script — a single shell command that restored the previous deployment image in under 10 seconds. The hosts break down how...

In episode 81 of The Software Engineering Podcast, Lucas and Luna explore how a senior DevOps engineer at a mid-sized SaaS company shrunk Docker images from 1.8 GB to under 90 MB — cutting deployment times by 70 percent and saving $12,000 a year in storage costs. They walk through the specific techniques used: multi-stage builds, Alpine base images, distroless runtimes, and layer optimisation. The...

Episode 80 of The Software Engineering Podcast dives into a specific cost-optimization story: how a senior engineer at a mid-size fintech company reduced their cloud logging bill by 90 percent — from $80,000 per month to under $8,000 — without sacrificing the signal their on-call team relied on. Lucas and Luna walk through the technical decisions: switching from structured JSON logging to a custom...