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Databases
SQL, NoSQL, schema design, migrations, ORMs, and database operations
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- Db Optimistic Locking> Optimistic locking assumes conflicts are rare, allows concurrent reads without locks, and detects conflicts at write time using version columns or conditional updates.Votes: 0GitHub stars: 20
- Db Nested Sets> Encoding hierarchy position with left/right boundary numbers for O(1) subtree and ancestor queries at the cost of expensive writes.Votes: 0GitHub stars: 20
- Db Mvcc> 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.Votes: 0GitHub stars: 20
- Db Migration Rollback> Forward-only vs reversible migrations, data backfill safety, and blue-green schema patterns for confident schema evolution.Votes: 0GitHub stars: 20
- Db Isolation Selection> Selecting the right isolation level requires matching the workload's correctness requirements against the performance cost and retry complexity of stricter levels.Votes: 0GitHub stars: 20
- Db Isolation Levels> The four SQL standard isolation levels control which concurrent transaction side-effects are visible, with PostgreSQL implementing them via MVCC snapshots rather than traditional locking.Votes: 0GitHub stars: 20
- Db Horizontal Sharding> Distributing rows of a table across multiple database instances (shards) to scale beyond the capacity of a single server, with careful attention to shard key selection and cross-shard query complexity.Votes: 0GitHub stars: 20
- Db Hierarchical Data> Choosing between adjacency list, nested sets, closure table, and materialized path based on read/write ratio, query patterns, and tree depth.Votes: 0GitHub stars: 20
- Db Hash Index> Optimized for equality-only lookups with O(1) average access time, hash indexes are smaller than B-tree when range queries and ordering are never needed.Votes: 0GitHub stars: 20
- Db Graph In Relational> Modeling vertices and edges in SQL tables for social graphs, dependency networks, and recommendation systems with recursive queries -- and knowing when SQL stops being practical.Votes: 0GitHub stars: 20
- Db First Normal Form> Every column holds a single atomic value, no repeating groups exist, and every row is uniquely identifiable by a primary key.Votes: 0GitHub stars: 20
- Db Expression Index> Indexes on computed expressions and specialized index types (GIN, GiST) for non-scalar data like JSONB, arrays, and full-text search.Votes: 0GitHub stars: 20
- Db Explain Reading> How to read query execution plans to identify performance bottlenecks, row count misestimations, and missing indexes.Votes: 0GitHub stars: 20
- Db Expand Contract> Add new structure, migrate data, remove old structure -- the three-phase pattern for safe column renames, type changes, and table restructuring.Votes: 0GitHub stars: 20
- Db Entity Attribute Value> A schema pattern for storing dynamic, user-defined attributes as rows instead of columns -- usually avoided in favor of JSONB or polymorphic alternatives, but occasionally justified for genuinely unbounded attribute sets.Votes: 0GitHub stars: 20
- Db Document In Relational> Using JSONB columns to store semi-structured data alongside relational tables, with indexing strategies and guidelines for when to embed vs normalize.Votes: 0GitHub stars: 20
- Db Denormalization> Intentionally introducing controlled redundancy into a normalized schema to eliminate expensive joins or aggregations, applied only after measured proof of a performance problem.Votes: 0GitHub stars: 20
- Db Deadlock Prevention> Deadlocks occur when two or more transactions hold locks and each waits for a lock the other holds; prevention through consistent lock ordering and detection through timeout-based abort resolves them.Votes: 0GitHub stars: 20
- Db Composite Index> Multi-column indexes that accelerate queries filtering on column combinations, governed by the leftmost prefix rule and the ESR (Equality, Sort, Range) column ordering strategy.Votes: 0GitHub stars: 20
- Db Closure Table> Storing all ancestor-descendant pairs in a separate table for O(1) subtree and ancestor lookups with manageable write costs.Votes: 0GitHub stars: 20
- Db Cap Theorem> In a distributed system, when a network partition occurs, you must choose between consistency (every read returns the most recent write) and availability (every non-failing node returns a response) -- you cannot have both simultaneously.Votes: 0GitHub stars: 20
- Db Audit Trail> Recording who changed what, when, and why, using trigger-based or application-level change tracking with immutable append-only logs.Votes: 0GitHub stars: 20
- Db Acid Properties> ACID guarantees that database transactions are processed reliably: each transaction is all-or-nothing (Atomic), leaves the database in a valid state (Consistent), operates as if no other transactions are running (Isolated), and once committed, persists even through crashes (Durable).Votes: 0GitHub stars: 20
- Db Acid In Practice> The mechanisms that make ACID guarantees real: Write-Ahead Logging ensures atomicity and durability, fsync ensures persistence to physical media, and crash recovery replays the WAL to restore a consistent state.Votes: 0GitHub stars: 20