System test center
Test sites focus
System test center
What is the system design?
System design need to know what knowledge?
How to design and implement a back-end system design services?
What is the system design? (System Design)
Definition of system design is a system architecture, modules, interfaces, and processes the data to meet the specific needs
eg: Design a short URL service, service reviews, Feed flow system, grab a red envelope system
A short URL service provides a service for all other uses: eg
Many micro-architecture service system is in accordance with the business split, the need for separate design a system service
The difficulty of system design
Senior engineer in the only way
- Need to have experience in related fields, algorithms, there is a certain architecture design capability
- Art are familiar with back-end component, eg: message queues, buffers, databases, frame
With writing, comprehensive ability flowcharting, architecture design, coding realization
Elements of the system design
Design three elements
Usage scenarios and limitations
Data Storage Design
Algorithm module design
What scenarios and conditions of use?
This system is used where?
eg: short URLs station system provides services to generate short URLs
Restrictions: the estimated number of users? At least be able to support the number of users (service)?
Concurrent estimate qps: Peak qps is how much? The average qps How much? (Requests per second and how much?)
Design data storage system
Selection Database
Demand design data table, which fields need, what type? Scale data growth
Database selection: the need for persistence? Use relational or NoSQL?
How to optimize? How to design an index? Can I use the cache?
Design algorithm related modules
System = + storage service
Interfaces need? How to interface design
What algorithm? Or the model?
The contrast between the pros and cons of different implementations, how to choose?
How to extend, fault-tolerant?
Users more, high qps how to deal with?
More than enough to keep data storage how to deal with?
How to deal with failure? Single point of failure, multi-point failure, avalanche problem
How to design and implement a short URL system?
What is the short URL system? What features (interfaces) contain?
Short URL storage design system? Which fields need to be stored?
How to design algorithm to generate a short URL?
What is the short URL system?
TinyUrl Service
To turn a long URL into a short URL service
After the conversion URL suffixes no more than seven (character or numeric)
Usage scenarios and limitations
Usage scenarios: Provides short URL services to each company's other business services
Function: a long URLs into short URLs and storing means, reducing the short long URL url
Requirements: a short URL suffix is not more than seven (uppercase and lowercase letters and numbers)
Estimated peak insert request of magnitude: several hundred, queries magnitude: Thousands
Data Storage Design
The need to design data is stored
Using Mysql to meet
What are the required fields?
How to design an index based on the query?
Mysql Data Sheet
| id | token (index) | url (original site) | created_at |
|---|---|---|---|
| 1 |
Algorithm design?
Short URL generation algorithm some? Compare the advantages and disadvantages?
two API： long2short_url, short2long_url
Increment id -?> Counters -> Use redis
request->redis incr index->encode(index)->save mysql
#递增序列算法
def mybin(num): #10进制->2进制
if num == 0:
return 0
res = []
while num:
num, rem = divmod(num, 2) # 2 -> 62
res.append(str(rem))
return ''.join(reversed(res))
print(mybin(10))
CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
def encode(num):
if num == 0:
return CHARS[0]
res = []
while num:
num, rem = divmod(num, len(CHARS)) #62
res.append(CHARS[rem])
return ''.join(reversed(res))
print(encode(1))
print(encode(61))Answer Key
Abide by the three elements to answer
Design includes data tables, api design, algorithm
Illustrated, there are data tables, interface definition, a flowchart
System Design Questions
How to design a spike system
Difficulties: How to deal with high concurrent user requests
What is a spike system?
How to design a spike system based on three elements mentioned?
Spike system which involves the back-end components