Claude Skills by Intense-Visions

> Forward-only vs reversible migrations, data backfill safety, and blue-green schema patterns for confident schema evolution.

> MVCC allows readers and writers to operate concurrently without blocking each other by maintaining multiple versions of each row, with visibility determined by transaction snapshots.

> Encoding hierarchy position with left/right boundary numbers for O(1) subtree and ancestor queries at the cost of expensive writes.

> Optimistic locking assumes conflicts are rare, allows concurrent reads without locks, and detects conflicts at write time using version columns or conditional updates.

> Indexes with a WHERE clause that index only a subset of rows, reducing size and improving performance for targeted query patterns.

> Pessimistic locking acquires locks before modifying data, guaranteeing exclusive access and preventing conflicts at the cost of reduced concurrency.

> Modeling inheritance hierarchies and type-varying relationships in relational databases using single-table inheritance (STI), class-table inheritance (CTI), or shared foreign key patterns.

> Structural query transformations that help the planner choose better execution plans without changing results.

> How the planner uses table statistics (pg_stats, histograms, most-common-values) to estimate row counts and choose execution plans.

> The SQL standard defines three read anomalies (dirty, non-repeatable, phantom) that isolation levels progressively prevent, plus PostgreSQL adds write skew as a fourth anomaly relevant to Serializable.

> Understanding when the planner chooses sequential scan, index scan, bitmap scan, or index-only scan and why each is optimal for different selectivity ranges.

> Every non-key column must depend on the entire composite primary key, not just part of it -- eliminating partial dependencies.

> Splitting a large table into smaller physical partitions by range, list, or hash to improve query performance, simplify maintenance, and enable efficient data lifecycle management.

> Modeling when facts are true (valid-time), when they were recorded (transaction-time), or both (bitemporal), enabling time-travel queries and regulatory audit.

> "Every non-key attribute must provide a fact about the key, the whole key, and nothing but the key." -- Codd's memorable definition of full normalization through 3NF.

> Designing append-heavy tables for metrics, events, and logs with time-based partitioning, retention policies, and efficient aggregation.

> Splitting a wide table into multiple narrower tables, separating hot columns from cold columns, and managing large objects with TOAST to reduce I/O and improve cache efficiency.

> Online schema changes that avoid table locks and keep the application serving traffic throughout the migration.

> Perceived actionability — signifiers, constraints, mappings (Don Norman), flat design's affordance problem, touch targets, hover states as affordance

> Visual order through edge alignment, center alignment, optical alignment, and the invisible structure that consistent alignment creates across a page

> Apple's design philosophy covering clarity/deference/depth, vibrancy and material effects, SF Symbols integration, semantic color system, safe area management, and platform-specific navigation patterns across iOS, iPadOS, macOS, watchOS, and visionOS.

> Composition methodology for building design systems using five distinct levels of abstraction: atoms, molecules, organisms, templates, and pages.

> Visual coherence across every touchpoint — mapping brand attributes to design decisions, voice-to-visual translation, consistency vs. monotony, brand flex zones, and multi-platform coherence

> Color independence — conveying information without relying on color alone, building colorblind-safe palettes, and ensuring perceptual uniformity across all vision types

> Color wheel relationships — complementary, analogous, triadic, split-complementary, tetradic schemes with usage guidance for building cohesive palettes

> Emotional and cultural associations of color — warmth/coolness, trust, urgency, industry conventions, and cultural variance for global product design

> Anatomy of reusable components covering slots, variants, states, sizes, composition vs configuration, compound components, and when to split vs merge.

> Internal vs. external consistency — maintaining coherent patterns within a product, adhering to platform conventions, and knowing when to break consistency deliberately

> Information density as a deliberate design variable — compact, comfortable, and spacious modes, matching density to user context, and the tradeoff between showing more and showing clearly

> Luminance contrast for readability and visual weight — WCAG ratios, contrast as a hierarchy tool, contrast beyond accessibility

> Color adaptation for dark themes — inverted hierarchy, reduced saturation, elevation through lightness, surface layering, and maintaining brand identity in dark contexts

> Data visualization principles — chart type selection, color encoding, annotation strategy, Tufte's data-ink ratio, accessible charts, avoiding chartjunk, and small multiples for comparison

> Evaluating existing design — heuristic evaluation (Nielsen's 10), consistency inventory, accessibility audit, competitive analysis, identifying and quantifying design debt

> Structured feedback — critique frameworks (like/wish/wonder, what/why/improve), separating subjective preference from objective assessment, avoiding "I don't like it"

> Documenting design decisions — design rationale, spec handoff, annotating designs, living documentation, decision logs, the DESIGN.md format

> Living system maintenance covering contribution models, deprecation processes, versioning strategies, adoption metrics, and documentation standards for treating a design system as a product.

> Depth as information — shadow anatomy (offset, blur, spread, color), elevation scale, chromatic shadows, material metaphor, dark mode shadows

> Empty and error state design — empty states as onboarding, error states as recovery, 404 pages, zero-data states, degraded states, constructive error messages

> System response design — immediate vs delayed feedback, optimistic updates, progress indicators, confirmation patterns, undo vs confirm, toast/snackbar/banner

> Microsoft's cross-platform design system covering the five foundational elements (light, depth, motion, material, scale), Acrylic and Mica materials, reveal highlight interactions, connected animations, responsive container strategies, and the Fluent 2 token theming architecture.

> Combining typefaces — contrast principles, superfamilies, serif+sans pairing rules, pairing by x-height and proportion, limiting to 2-3 families

> Form design beyond labels — progressive disclosure, inline validation timing, smart defaults, forgiving formats, single-column superiority, error recovery

> Pattern completion — the brain fills gaps in incomplete shapes (closure) and follows smooth paths over abrupt changes (continuity), with implications for icons, progress indicators, and visual flow

> Motion grouping — elements that move or change together are perceived as a unit, with implications for animation, loading states, and batch operations

> Depth perception — distinguishing foreground from background, ambiguous figure-ground as a design tool, z-axis ordering, overlay and modal perception

> Spatial grouping — elements near each other are perceived as related, controlling group membership through distance, with common region as a proximity amplifier

> Visual kinship — elements sharing color, size, shape, or texture are perceived as related, creating categories without explicit labels

> Grid theory — column, modular, baseline, and compound grids, gutter rhythm, and breaking the grid intentionally for emphasis

> Designing for internationalization — text expansion, RTL layout, icon cultural sensitivity, date/number/currency formatting, pseudolocalization testing

> Icon design principles — optical sizing, stroke consistency, pixel grid alignment, metaphor clarity, icon families, filled vs outlined states, and icon as a systematic visual language