File uploads are attacker-controlled input with extra surface area. I validate extension and MIME type, rename everything server side, scan risky formats, and keep user uploads out of executable paths. If the business allows arbitrary uploads, storage

Spring's @Transactional manages database transactions declaratively. Transaction propagation controls behavior when methods call other transactional methods—REQUIRED, REQUIRESNEW, NESTED. Isolation levels prevent concurrent access issues—READUNCOMMITT

I spend a few minutes standardizing plotting defaults before I start analysis. Better typography, clear labels, and consistent palette choices reduce review cycles and improve notebook readability. Charts should explain themselves without requiring a

Flexbox provides one-dimensional layout for rows or columns. I use display: flex on containers to enable flexbox. The flex-direction property controls main axis direction (row, column, row-reverse, column-reverse). The justify-content property aligns

Rate limiting is both a security control and an availability control. I use it to slow credential stuffing, login brute force, and noisy scraping without punishing normal use. The trick is keying limits on the right dimensions and emitting metrics so

CSS transitions animate property changes with transition: property duration timing-function delay. I use transition-property to specify which properties animate. The timing-function controls acceleration with values like ease, ease-in, ease-out, cubic

Google Play Billing enables selling digital content and subscriptions. I integrate the Play Billing Library and initialize BillingClient with PurchasesUpdatedListener. Query available products with queryProductDetailsAsync(). Launch purchase flow with

UserDefaults provides simple key-value storage for app preferences and settings. It persists basic types like strings, numbers, bools, dates, and data automatically. I use UserDefaults for user preferences, app state, and feature flags—never for sensi

Feature flags (feature toggles) enable/disable functionality without code deployment. I use libraries like Togglz or FF4J for flag management. Flags support A/B testing, canary releases, and emergency kill switches. Strategy pattern determines flag st

Spring Batch handles large-scale batch processing—ETL, data migration, report generation. Jobs contain steps; steps have readers, processors, and writers. Chunk-oriented processing reads, processes, and writes data in configurable batches. ItemReader

CORS (Cross-Origin Resource Sharing) controls which domains can access APIs. Browsers enforce same-origin policy by default. I configure allowed origins, methods, headers, and credentials. @CrossOrigin enables CORS per controller or method. Global con

Custom ViewGroups enable specialized layout behavior beyond standard containers. I extend ViewGroup and override onMeasure() to measure children and onLayout() to position them. measureChild() or measureChildWithMargins() determines child sizes. Layou