Tauseef FayyazA to Z
Glossary
Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.
A
- Access patterns
- The questions an app asks its data again and again, such as "get user by email" or "last 20 orders for a shop", with a rough idea of how often each runs.
- ACID transactions
- A transaction groups changes so they are atomic (all or nothing), consistent (rules hold), isolated (concurrent transactions do not interfere) and durable (saved once committed).
C
- Consistency needs
- How correct data must be at every moment.
- Constraints
- Rules the database enforces on every write: NOT NULL, UNIQUE, CHECK and foreign keys, which make a value refer to an existing row in another table.
D
- Decision chart: data and access pattern to database
- A quick map from the kind of data and the way it is used to the database type that usually fits.
J
- JSON columns
- Columns that store JSON inside a relational table.
M
- Migrations, drivers and ORMs
- A driver sends queries from your code; an ORM maps tables to objects.
- MySQL, SQLite and SQL Server
- MySQL is common behind websites and PHP apps.
O
- One Postgres is often enough
- One PostgreSQL database with
jsonb, full-text search, pgvector, and TimescaleDB or PostGIS when needed covers relational data, flexible fields, search, similarity, time series and locations.
P
- PostgreSQL as the default
- PostgreSQL is an open source relational database that also stores and indexes JSON, has built-in full-text search and gains vectors, maps and time series through extensions.
Q
- Questions to ask before choosing
- A short list answered for every project: data shapes, top access patterns, size after a year, what must be exact, any search, similarity or reporting needs, where it runs, and who will look after it.
R
- Read-write mix and data size
- Whether an app mostly reads or mostly writes, how many records it will hold after a year and how big each one is.
- Relational database
- A database that stores data in tables of rows and columns, links tables with keys and is queried with SQL.
S
- Structured, semi-structured and unstructured data
- Structured data fits rows and columns with known types.