SystemsExpert Flashcards
Latency
The time it takes for a certain operation to complete in a system.
What are the orders of magnitude for latency?
Reading 1MB from: RAM == 250us (.25sec) SSD == 1 ms Transferring 1MB over a network == 10 ms HDD == 20 ms Intercontinental Round Trip == 150 ms
Throughput
The number of operations that a system can handle er time unit…for example, the throughput of a server cna be measured in requests/second.
IP
Internet protocol. This network protocol outlines how almost all machine to machine communications should happen in the world. Other protocols like TCP, UDP, and HTTP are built on top of this protocol.
TCP
Transmission Control Protocol, allows for ordered, reliable data delivery between machines over the public network.. exposes sockets to applications that they can use to stream data through an open connection.
HTTP
Clients make requests and servers respond with responses. Requests have headers, host, port, method, body.
IP Packet
Smallest unit of data being sent over IP. Consists of IP header and a payload.
Availability
The probability of a particular service being up and running at any particular point in time.
High Availability
Means they are operational at 5 nines or more.
Redundancy
The act of replicating parts of a system in an effort to make it more reliable.
Cache
Piece of hardware or software that stores data, meant to retrieve data faster.
Often used to store responses to network requests.
Cache hit
When requested data is found in a cache.
Cache miss
When data could have been found in the cache, but it wasn’t…it’s a negative consequence of a system.
Cache eviction policy
The policy by which values get removed or evicted from a cache.
What are popular cache eviction policies?
LRU (least recently used), FIFO (First in, first out), LFU (Least frequently used)
