Glossary

A comprehensive glossary of terms used throughout this knowledge base.

A

Term	Definition
ACID	Atomicity, Consistency, Isolation, Durability — properties guaranteeing reliable database transactions
ALU	Arithmetic Logic Unit — digital circuit performing arithmetic and bitwise operations
API	Application Programming Interface — set of protocols for building software
ARP	Address Resolution Protocol — maps IP addresses to MAC addresses
ASLR	Address Space Layout Randomization — security technique randomizing memory addresses
AVX	Advanced Vector Extensions — SIMD instruction set for x86 CPUs

B

Term	Definition
B+ Tree	Self-balancing tree structure optimized for disk-based indexing
BBR	Bottleneck Bandwidth and Round-trip propagation time — TCP congestion control algorithm
BCNF	Boyce-Codd Normal Form — stricter version of 3NF
BIOS	Basic Input/Output System — firmware for hardware initialization
BGP	Border Gateway Protocol — protocol for routing between autonomous systems
Btrfs	B-tree file system — modern Linux copy-on-write filesystem

C

Term	Definition
Cache	Small, fast memory storing frequently accessed data
CAP Theorem	States a distributed system can guarantee only 2 of: Consistency, Availability, Partition tolerance
CAS	Compare-and-Swap — atomic operation for lock-free programming
CDN	Content Delivery Network — distributed servers for content delivery
CIDR	Classless Inter-Domain Routing — IP address allocation method
CISC	Complex Instruction Set Computing
COW	Copy-on-Write — optimization deferring copies until modification
CFS	Completely Fair Scheduler — Linux default process scheduler
CPU	Central Processing Unit
CTE	Common Table Expression — named temporary result set in SQL

D

Term	Definition
DMA	Direct Memory Access — allows hardware to access memory without CPU
DNS	Domain Name System — translates domain names to IP addresses
DRAM	Dynamic Random-Access Memory
DAC	Discretionary Access Control

E

Term	Definition
EEPROM	Electrically Erasable Programmable Read-Only Memory
epoll	Linux I/O event notification facility
ext4	Fourth extended filesystem — default Linux filesystem

F

Term	Definition
FCFS	First-Come, First-Served scheduling
FIFO	First-In, First-Out
FUSE	Filesystem in Userspace
FLP	Fischer-Lynch-Paterson impossibility result

G

Term	Definition
GiST	Generalized Search Tree — PostgreSQL index type
GIN	Generalized Inverted Index — PostgreSQL index type
GPU	Graphics Processing Unit

H

Term	Definition
HBM	High Bandwidth Memory
HDD	Hard Disk Drive
Huge Pages	Large memory pages (2MB or 1GB) reducing TLB misses
HTTP	Hypertext Transfer Protocol

I

Term	Definition
I/O	Input/Output
ICMP	Internet Control Message Protocol
IEEE 754	Standard for floating-point arithmetic
IOPS	Input/Output Operations Per Second
ISA	Instruction Set Architecture
ISR	Interrupt Service Routine

K

Term	Definition
Kernel	Core component of an OS managing hardware and system resources

L

Term	Definition
LRU	Least Recently Used — cache/page replacement policy
LFU	Least Frequently Used
LSM	Log-Structured Merge-tree — storage engine data structure
LKM	Loadable Kernel Module

M

Term	Definition
MAC	Media Access Control address
MESI	Modified, Exclusive, Shared, Invalid — cache coherence protocol
Mmap	Memory-mapped file
MLFQ	Multilevel Feedback Queue scheduling
MVCC	Multi-Version Concurrency Control

N

Term	Definition
NAT	Network Address Translation
NUMA	Non-Uniform Memory Access
NVMe	Non-Volatile Memory Express
NVM	Non-Volatile Memory

O

Term	Definition
OOO	Out-of-Order execution
OSPF	Open Shortest Path First — routing protocol

P

Term	Definition
PCB	Process Control Block
PCIe	Peripheral Component Interconnect Express
Paxos	Consensus algorithm for distributed systems
POSIX	Portable Operating System Interface

Q

Term	Definition
QUIC	Quick UDP Internet Connections — transport protocol

R

Term	Definition
RAID	Redundant Array of Independent Disks
RISC	Reduced Instruction Set Computing
RIP	Routing Information Protocol
Raft	Understandable consensus algorithm

S

Term	Definition
SLAB	Linux kernel memory allocator
SMP	Symmetric Multiprocessing
SMT	Simultaneous Multithreading (Hyperthreading)
SRAM	Static Random-Access Memory
SSD	Solid State Drive
STAR	Situation, Task, Action, Result — behavioral interview framework

T

Term	Definition
TCP	Transmission Control Protocol
TLB	Translation Lookaside Buffer
TLS	Transport Layer Security
TSC	Time Stamp Counter

U

Term	Definition
UDP	User Datagram Protocol
UEFI	Unified Extensible Firmware Interface

V

Term	Definition
VFS	Virtual File System
VM	Virtual Machine
VPN	Virtual Private Network
VPC	Virtual Private Cloud

W

Term	Definition
WAL	Write-Ahead Logging
WSS	Working Set Size

X

Term	Definition
XFS	High-performance filesystem

Z

Term	Definition
ZFS	Zettabyte File System
ZAB	ZooKeeper Atomic Broadcast