⏱ 9 min read A cursor-based incremental sync system lets clients efficiently download only the data that has changed since their last sync, rather […] Read article

⏱ 8 min read A webhook delivery system pushes event notifications to customer-configured HTTP endpoints — the foundation of Stripe, GitHub, Shopify, and Twilio’s Read article

⏱ 9 min read A referral tracking system attributes new user signups to the existing user who referred them, enabling reward programs and measuring Read article

⏱ 9 min read A poll system lets users create questions with multiple choice answers, vote on them, and see real-time results. Used in Read article

⏱ 8 min read A bookmark (save) system lets users collect and organize content they want to revisit — articles, products, listings, posts. Core Read article

⏱ 10 min read A content tagging system lets users and systems attach descriptive labels to content — blog posts, products, images, videos — Read article

⏱ 9 min read A content reporting and abuse detection system allows users to flag harmful content — spam, harassment, hate speech, illegal material Read article

⏱ 8 min read An idempotency key service ensures that retried API requests do not cause duplicate side effects — a critical requirement for Read article

⏱ 10 min read Multi-factor authentication (MFA) adds a second verification layer beyond passwords — protecting accounts even when passwords are compromised. The three Read article

⏱ 9 min read Cache warming ensures a cache is pre-populated with frequently accessed data before users experience cache misses. Without warming, a fresh Read article

⏱ 8 min read A trending topics system surfaces content gaining rapid engagement — the top hashtags on Twitter, trending searches on Google, or Read article

⏱ 9 min read A follower graph stores directed relationships between users — Alice follows Bob, but Bob may not follow Alice. It powers Read article

⏱ 8 min read An order tracking system maintains the lifecycle of a purchase from placement through delivery, providing real-time status to customers and Read article

⏱ 9 min read A payment processing pipeline accepts customer payment details, communicates with a payment processor (Stripe, Braintree, Adyen), and reliably records the Read article

⏱ 8 min read A user presence system tracks whether users are online, offline, or idle — powering the green dots in Slack, WhatsApp, Read article