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Databases
SQL, NoSQL, schema design, migrations, ORMs, and database operations
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- VerboseA window function computes an aggregate or ranking *over a set of rows related to the current row*, without collapsing them the way `GROUP BY` does. The `OVER` clause defines the window; `PARTITION BY` splits rows into independent groups, and `ORDER BY` orders rows within each partition.Votes: 0GitHub stars: 2
- MinimalTechniques for diagnosing and optimizing slow SQL queries.Votes: 0GitHub stars: 2
- Verbose**When:** Not important (contact info) **Implementation:** ```sql UPDATE dim_customer SET email = 'newemail@example.com' WHERE customer_id = 123; ```Votes: 0GitHub stars: 2
- VerboseA stakeholder asks to make search faster. As stated this cannot be started, finished, or verified. Decomposition is the work of converting it into a tree whose leaves each have an owner, a size, and a number that says when they are done.Votes: 0GitHub stars: 2
- MinimalTurn a vague request into a tree of sub-problems that are individually measurable, independently solvable, and small enough to finish.Votes: 0GitHub stars: 2
- VerboseRelational modelling lets you defer query design: normalize the entities, and the optimizer will find a plan for whatever you ask later. Non-relational stores remove that safety net. There is no join and often no ad-hoc filter, so the physical layout *is* the query plan. Design it from the queries or you will discover, in production, that a required read is impossible without a full scan.Votes: 0GitHub stars: 2
- MinimalChoose a non-relational store by starting from the queries you must serve, not from the shape of your entities or a scale number you have not yet reached.Votes: 0GitHub stars: 2
- MinimalChoose how services talk to each other, given that every synchronous call adds latency and borrows the callee's availability.Votes: 0GitHub stars: 2
- VerboseThe most expensive database mistakes are made before a single row is written, by choosing the engine from familiarity or hype and then discovering the data does not fit. Invert it. Write down the access pattern first:Votes: 0GitHub stars: 2
- MinimalChoose a managed database by the access pattern the data will actually see — not by which engine is most familiar or most talked about.Votes: 0GitHub stars: 2
- Verbose**Pattern:** ```sql -- Idempotency via unique constraint CREATE TABLE orders ( customer_id INT, order_timestamp TIMESTAMP, amount DECIMAL, UNIQUE (customer_id, order_timestamp) );Votes: 0GitHub stars: 2
- Verbose``` User Request ↓ API Gateway (span: api-request) ├─ Authenticate (span: auth) ├─ Validate (span: validate) └─ Route to Service (span: route) ↓ Application Service (span: process-order) ├─ Database query (span: db-select) ├─ Cache lookup (span: cache-get) └─ External API call (span: payment-api) ↓ Trace contains all spans with timing ```Votes: 0GitHub stars: 2
- VerboseThe default, because it fails open: when the cache is unavailable, reads still succeed against the source of truth, just slower.Votes: 0GitHub stars: 2
- MinimalAdd a shared cache that actually reduces load and latency, without serving stale data or collapsing the origin the moment the cache misses.Votes: 0GitHub stars: 2
- Minimal``` Time | Product -----> Fact Table <----- Customer | Geography ```Votes: 0GitHub stars: 2
- VerboseThe relevant axis is not "how do we deploy" but "how fast and how cheaply can we undo". Everything else follows from that.Votes: 0GitHub stars: 2
- Minimal```sql CREATE TABLE orders ( order_id INT, customer_id INT, amount DECIMAL ) PARTITION BY RANGE (YEAR(created_at)) ( PARTITION p2024 VALUES LESS THAN (2025), PARTITION p2025 VALUES LESS THAN (2026), PARTITION p2026 VALUES LESS THAN (2027) ); ```Votes: 0GitHub stars: 2
- Verbose`await` does not block a thread. It registers the rest of the method as a continuation, returns control to the caller, and resumes when the awaited task completes. The thread is free to do other work in the meantime — that is the whole point of async I/O.Votes: 0GitHub stars: 2
- MinimalWrite async code that doesn't deadlock, and LINQ queries that run once, in the right place (in memory vs. in the database).Votes: 0GitHub stars: 2
- MinimalChoose between precomputing predictions on a schedule and computing them per request — a decision driven by how fresh the *inputs* must be, not by how modern the architecture looks.Votes: 0GitHub stars: 2
- VerboseRBAC assigns permissions to roles and roles to subjects. The discipline that keeps it maintainable is that application code asks about *permissions*, never about role names.Votes: 0GitHub stars: 2
- Slowly Changing Dimensions**When:** Not important (contact info)Votes: 0GitHub stars: 2
- Problem DecompositionA stakeholder asks to make search faster.Votes: 0GitHub stars: 2
- Nosql Database SelectionRelational modelling lets you defer query design: normalize the entities, andVotes: 0GitHub stars: 2