Multi stage building strategy & Docker Image scanning

 multi-stage building strategy 
=====================
1.build the code-------------->stage:1
2.check the code quality
3.store the build artifact into NEXUS
4.create a docker image------->stage:2
5.scan the docker image
6.store the docker image into NEXUS
7.pull the docker image
8.scan docker image 
9.deploy into DEV,QA,STAGING,PROD with step by step approval gates

SCAN THE DOCKER IMAGES  
======================
docker images will be scanned in two stages
1.stage:1--->after build artifact 
             we create an image 
             we scan the image
             if everything is good
             Image will be stored into NEXUS REPO
             WE SCAN THE IMAGE before uploading into NEXUS
2.stage:2--->we pull the image from the NEXUS REPO
             we scan the image
             if everything is good or PASS
             image will be deployed into DEV Environment
             WE SCAN THE IMAGE before deploy into DEV Environment
in my project we used Trivy software tool for image scanning..
in my project generally , we follow multi stage build approach 
what is multi stage build approach pls explain 
==============================================
1st stage:
----------
we build the code in 1st stage
and we get the build file or build artifact
this is stage 1 build process
2nd stage:
----------
after that we take this build file or build artificat 
then we create a lightweight image 
this is stage 2 build process
this is also called as final build process 

 1.Trivy
 2.Aqua Security
 3.Synk
 4.Grype
 5.cloud editions

1.without scan can you upload this image into NEXUS ?
  Ans:No , we must scan 
2.without scan can you deploy this image into DEV ?
  Ans:No , we must scan