<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
blue-green	O
(	O
also	O
blue/green	O
)	O
deployment	O
is	O
a	O
method	O
of	O
installing	O
changes	O
to	O
a	O
web	O
,	O
app	O
,	O
or	O
database	O
server	O
by	O
swapping	O
alternating	O
production	O
and	O
staging	O
servers	O
.	O
</s>
<s>
In	O
blue-green	B-Application
deployments	I-Application
,	O
two	O
servers	O
are	O
maintained	O
:	O
a	O
"	O
blue	O
"	O
server	O
and	O
a	O
"	O
green	O
"	O
server	O
.	O
</s>
<s>
At	O
any	O
given	O
time	O
,	O
only	O
one	O
server	O
is	O
handling	O
requests	O
(	O
e.g.	O
,	O
being	O
pointed	O
to	O
by	O
the	O
DNS	B-Application
)	O
.	O
</s>
