<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
the	O
terms	O
frontend	B-Architecture
and	I-Architecture
backend	I-Architecture
(	O
or	O
sometimes	O
referred	O
to	O
as	O
back	B-Architecture
end	I-Architecture
or	O
back-end	B-Architecture
)	O
refer	O
to	O
the	O
separation	O
of	O
concerns	O
between	O
the	O
presentation	B-Application
layer	I-Application
(	O
frontend	B-Architecture
)	O
,	O
and	O
the	O
data	B-Application
access	I-Application
layer	I-Application
(	O
backend	B-Architecture
)	O
of	O
a	O
piece	O
of	O
software	O
,	O
or	O
the	O
physical	O
infrastructure	O
or	O
hardware	B-Device
.	O
</s>
<s>
In	O
the	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
,	O
the	O
client	B-Protocol
is	O
usually	O
considered	O
the	O
frontend	B-Architecture
and	O
the	O
server	B-Application
is	O
usually	O
considered	O
the	O
backend	B-Architecture
,	O
even	O
when	O
some	O
presentation	O
work	O
is	O
actually	O
done	O
on	O
the	O
server	B-Application
itself	O
.	O
</s>
<s>
In	O
software	B-Architecture
architecture	I-Architecture
,	O
there	O
may	O
be	O
many	O
layers	B-Architecture
between	O
the	O
hardware	B-Device
and	O
end	O
user	O
.	O
</s>
<s>
The	O
front	O
is	O
an	O
abstraction	O
,	O
simplifying	O
the	O
underlying	O
component	O
by	O
providing	O
a	O
user-friendly	B-General_Concept
interface	O
,	O
while	O
the	O
back	O
usually	O
handles	O
data	O
storage	O
and	O
business	B-Architecture
logic	I-Architecture
.	O
</s>
<s>
A	O
rule	O
of	O
thumb	O
is	O
that	O
the	O
client-side	B-Operating_System
(	O
or	O
"	O
frontend	B-Architecture
"	O
)	O
is	O
any	O
component	O
manipulated	O
by	O
the	O
user	O
.	O
</s>
<s>
The	O
server-side	O
(	O
or	O
"	O
backend	B-Architecture
"	O
)	O
code	O
usually	O
resides	O
on	O
the	O
server	B-Application
,	O
often	O
far	O
removed	O
physically	O
from	O
the	O
user	O
.	O
</s>
<s>
In	O
content	B-Protocol
management	I-Protocol
systems	I-Protocol
,	O
the	O
terms	O
frontend	B-Architecture
and	I-Architecture
backend	I-Architecture
may	O
refer	O
to	O
the	O
end-user	O
facing	O
views	O
of	O
the	O
CMS	O
and	O
the	O
administrative	O
views	O
,	O
respectively	O
.	O
</s>
<s>
In	O
speech	B-Application
synthesis	I-Application
,	O
the	O
frontend	B-Architecture
refers	O
to	O
the	O
part	O
of	O
the	O
synthesis	O
system	O
that	O
converts	O
the	O
input	O
text	O
into	O
a	O
symbolic	O
phonetic	O
representation	O
,	O
and	O
the	O
backend	B-Architecture
converts	O
the	O
symbolic	O
phonetic	O
representation	O
into	O
actual	O
sounds	O
.	O
</s>
<s>
In	O
compilers	B-Language
,	O
the	O
frontend	B-Architecture
translates	B-Application
a	O
computer	O
programming	O
source	O
code	O
into	O
an	O
intermediate	B-Application
representation	I-Application
,	O
and	O
the	O
backend	B-Architecture
works	O
with	O
the	O
intermediate	B-Application
representation	I-Application
to	O
produce	O
code	O
in	O
a	O
computer	O
output	O
language	O
.	O
</s>
<s>
The	O
backend	B-Architecture
usually	O
optimizes	O
to	O
produce	O
code	O
that	O
runs	O
faster	O
.	O
</s>
<s>
The	O
frontend/backend	O
distinction	O
can	O
separate	O
the	O
parser	B-Language
section	O
that	O
deals	O
with	O
source	O
code	O
and	O
the	O
backend	B-Architecture
that	O
generates	B-Application
code	I-Application
and	I-Application
optimizes	I-Application
.	O
</s>
<s>
Some	O
designs	O
,	O
such	O
as	O
GCC	B-Application
,	O
offer	O
choices	O
between	O
multiple	O
frontends	B-Architecture
(	O
parsing	B-Language
different	O
source	O
languages	O
)	O
or	O
backends	B-Architecture
(	O
generating	O
code	O
for	O
different	O
target	O
processors	B-General_Concept
)	O
.	O
</s>
<s>
Some	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
applications	O
running	O
in	O
a	O
desktop	O
environment	O
are	O
implemented	O
as	O
a	O
thin	O
frontend	B-Architecture
for	O
underlying	O
command-line	B-Application
interface	I-Application
(	O
CLI	O
)	O
programs	O
,	O
to	O
save	O
the	O
user	O
from	O
learning	O
the	O
special	O
terminology	O
and	O
memorizing	O
the	O
commands	B-Application
.	O
</s>
<s>
Another	O
way	O
to	O
understand	O
the	O
difference	O
between	O
the	O
two	O
is	O
to	O
understand	O
the	O
knowledge	O
required	O
of	O
a	O
frontend	B-Architecture
vs.	O
a	O
backend	B-Architecture
software	B-Application
developer	I-Application
.	O
</s>
<s>
The	O
list	O
below	O
focuses	O
on	O
web	B-General_Concept
development	O
as	O
an	O
example	O
.	O
</s>
<s>
Web	B-General_Concept
performance	O
(	O
largest	O
contentful	O
paint	O
,	O
time	O
to	O
interactive	O
,	O
60	O
FPS	O
animations	O
and	O
interactions	O
,	O
memory	O
usage	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
frontend	B-Architecture
communicates	O
with	O
backend	B-Architecture
through	O
an	O
API	B-Application
.	O
</s>
<s>
In	O
the	O
case	O
of	O
web	B-General_Concept
and	O
mobile	O
frontends	B-Architecture
,	O
the	O
API	B-Application
is	O
often	O
based	O
on	O
HTTP	B-Protocol
request/response	O
.	O
</s>
<s>
The	O
API	B-Application
is	O
sometimes	O
designed	O
using	O
the	O
"	O
Backend	B-Architecture
for	O
Frontend	B-Architecture
"	O
(	O
BFF	O
)	O
pattern	O
,	O
that	O
serves	O
responses	O
to	O
ease	O
the	O
processing	O
on	O
frontend	B-Architecture
side	O
.	O
</s>
<s>
In	O
network	B-Architecture
computing	I-Architecture
,	O
frontend	B-Architecture
can	O
refer	O
to	O
any	O
hardware	B-Device
that	O
optimizes	O
or	O
protects	O
network	O
traffic	O
.	O
</s>
<s>
It	O
is	O
called	O
application	B-Architecture
front-end	I-Architecture
hardware	B-Device
because	O
it	O
is	O
placed	O
on	O
the	O
network	O
's	O
outward-facing	B-General_Concept
frontend	I-General_Concept
or	I-General_Concept
boundary	I-General_Concept
.	O
</s>
<s>
Network	O
traffic	O
passes	O
through	O
the	O
front-end	B-Architecture
hardware	B-Device
before	O
entering	O
the	O
network	O
.	O
</s>
<s>
In	O
processor	B-General_Concept
design	I-General_Concept
,	O
frontend	B-Architecture
design	O
would	O
be	O
the	O
initial	O
description	O
of	O
the	O
behavior	O
of	O
a	O
circuit	O
in	O
a	O
hardware	B-Device
description	O
language	O
such	O
as	O
Verilog	B-Language
,	O
while	O
backend	B-Architecture
design	O
would	O
be	O
the	O
process	O
of	O
mapping	O
that	O
behavior	O
to	O
physical	O
transistors	O
on	O
a	O
die	O
.	O
</s>
