Tag
#engineering-logs
4 articles
01RAG Retrieval Strategies on a 50k-Document Dataset: BM25 vs Dense vs Hybrid
How BM25, dense embeddings and hybrid search (RRF) behave on a 50k-document RAG corpus: working code, honest trade-offs, and when each one actually wins.
11 minThe Engineering Logs
02The Discount That Knew You Were Hesitating: Rule-Based Personalisation in an Online Pharmacy
How Zovita+ turns browsing into personal discounts without a machine-learning model: one visitor key for guests and customers, interaction counters, six offer rules, one pricing function for the bag and the charge, offers locked and redeemed once at checkout, guest-to-account merging, A/B tests, and the edge cases that shaped it.
10 minThe Engineering Logs
03One Seat, Two Buyers: Race Conditions, IDOR and Keys in a Cinema Booking System
How BookMyMovie makes sure one cinema seat is never sold twice, a guessed booking number shows nothing, and a leaked or missing key can't quietly break tickets: row locks, lock order, a NULL-tolerant unique key, status compare-and-set, idempotency, IDOR scoping, HMAC tickets, captcha step-up, and the bugs that still got through.
11 minThe Engineering Logs
04The Last Mango Problem: Race Conditions in a Real Marketplace
What happens when fifty people try to buy the last item, use a single-use coupon or book a nearly full pickup window at the same instant, the MySQL snapshot detail that almost overbooked a stall, and the quieter races that hide in stock forms, restocks and payments.
10 minThe Engineering Logs