<s>
YDB	B-Operating_System
(	O
Yet	O
another	O
DataBase	O
)	O
is	O
a	O
distributed	B-Language
SQL	I-Language
database	B-Application
management	I-Application
system	I-Application
(	O
DBMS	O
)	O
developed	O
by	O
Yandex	O
,	O
available	O
as	O
open-source	B-License
technology	I-License
.	O
</s>
<s>
YDB	B-Operating_System
is	O
a	O
technology	O
that	O
allows	O
creating	O
large	O
web	O
services	O
capable	O
of	O
supporting	O
large	O
operational	O
loads	O
of	O
up	O
to	O
millions	O
requests	O
per	O
second	O
.	O
</s>
<s>
It	O
uses	O
a	O
strongly	O
typed	O
dialect	O
of	O
SQL	B-Language
—	O
YDB	B-Operating_System
Query	O
Language	O
(	O
YQL	O
)	O
as	O
a	O
default	O
query	O
language	O
and	O
supports	O
ACID	O
transactions	O
.	O
</s>
<s>
The	O
closest	O
analogues	O
of	O
this	O
DBMS	O
available	O
as	O
open-source	B-License
software	O
are	O
YugabyteDB	B-Operating_System
and	O
CockroachDB	B-Operating_System
.	O
</s>
<s>
YDB	B-Operating_System
can	O
be	O
either	O
self-deployed	O
to	O
computer	B-Architecture
clusters	I-Architecture
across	O
physical	O
hosts	B-Device
or	O
on	O
virtual	B-Architecture
machines	I-Architecture
via	O
Kubernetes	B-General_Concept
or	O
as	O
a	O
managed	O
service	O
in	O
Yandex	O
Cloud	O
.	O
</s>
<s>
Serverless	B-General_Concept
computing	I-General_Concept
mode	O
or	O
dedicated	O
mode	O
are	O
available	O
for	O
the	O
managed	O
service	O
option	O
.	O
</s>
<s>
YDB	B-Operating_System
works	O
on	O
clusters	O
with	O
shared-nothing	B-Operating_System
architecture	I-Operating_System
and	O
uses	O
standard	O
commodity	B-Device
hardware	I-Device
.	O
</s>
<s>
Functionally	O
,	O
this	O
protocol	O
is	O
similar	O
to	O
Paxos	B-Operating_System
and	O
Raft	B-Operating_System
.	O
</s>
<s>
User	O
tablets	O
in	O
YDB	B-Operating_System
have	O
a	O
mandatory	O
primary	O
key	O
and	O
are	O
sharded	O
by	O
its	O
ranges	O
.	O
</s>
<s>
Distributed	O
Storage	O
ensures	O
data	O
replication	O
,	O
while	O
data	O
from	O
tablets	O
is	O
stored	O
as	O
BLOBs	B-General_Concept
.	O
</s>
<s>
YDB	B-Operating_System
executes	O
distributed	O
transactions	O
between	O
data	O
from	O
one	O
or	O
more	O
tables	O
using	O
a	O
distributed	O
transaction	O
framework	O
based	O
on	O
the	O
Calvin	O
algorithm	O
.	O
</s>
<s>
Unlike	O
Calvin	O
,	O
YDB	B-Operating_System
supports	O
interactive	O
and	O
non-deterministic	O
transactions	O
by	O
using	O
record	B-Operating_System
locking	I-Operating_System
.	O
</s>
<s>
YDB	B-Operating_System
is	O
based	O
on	O
the	O
actor	B-Application
model	I-Application
.	O
</s>
<s>
Actors	O
are	O
single-threaded	O
back-end	O
automats	O
that	O
exchange	O
messages	O
with	O
each	O
other	O
while	O
residing	O
on	O
different	O
cluster	B-Architecture
servers	I-Architecture
.	O
</s>
<s>
A	O
number	O
of	O
digital	O
services	O
,	O
such	O
as	O
virtual	O
block	O
devices	O
or	O
persistent	O
queues	O
,	O
have	O
been	O
developed	O
as	O
a	O
layer	O
over	O
YDB	B-Operating_System
.	O
</s>
<s>
YDB	B-Operating_System
supports	O
user	O
interaction	O
via	O
the	O
gRPC	B-Application
protocol	O
with	O
several	O
client	O
SDKs	O
implementing	O
procedures	O
for	O
node	O
discovery	O
,	O
client	O
balancing	O
,	O
etc	O
.	O
</s>
<s>
YDB	B-Operating_System
does	O
not	O
support	O
UUID	O
as	O
standalone	O
data	O
type	O
.	O
</s>
<s>
In	O
2010	O
,	O
Yandex	O
started	O
working	O
on	O
its	O
own	O
NoSQL	B-General_Concept
DBMS	O
KiWi	O
and	O
rolled	O
it	O
out	O
for	O
internal	O
use	O
in	O
2011	O
.	O
</s>
<s>
However	O
,	O
KiWi	O
had	O
eventual	B-General_Concept
consistency	I-General_Concept
,	O
as	O
well	O
as	O
other	O
disadvantages	O
of	O
the	O
NoSQL	B-General_Concept
model	O
.	O
</s>
<s>
In	O
2012	O
,	O
to	O
cover	O
its	O
needs	O
for	O
DBMS	O
,	O
Yandex	O
starts	O
the	O
KiKiMR	O
project	O
,	O
which	O
later	O
becomes	O
known	O
as	O
YDB	B-Operating_System
.	O
</s>
<s>
In	O
2016	O
,	O
YDB	B-Operating_System
was	O
rolled	O
out	O
to	O
Yandex	O
services	O
.	O
</s>
<s>
In	O
2018	O
,	O
the	O
Yandex	O
Cloud	O
platform	O
was	O
launched	O
with	O
data	O
storage	O
based	O
on	O
YDB	B-Operating_System
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
the	O
company	O
announced	O
that	O
in	O
the	O
future	O
it	O
would	O
make	O
YDB	B-Operating_System
available	O
as	O
a	O
managed	O
service	O
in	O
Yandex	O
Cloud	O
,	O
and	O
later	O
provided	O
customers	O
with	O
access	O
to	O
this	O
service	O
,	O
as	O
well	O
as	O
other	O
managed	O
services	O
,	O
such	O
as	O
PostgreSQL	O
,	O
MongoDB	O
and	O
others	O
.	O
</s>
<s>
This	O
cloud	O
version	O
was	O
called	O
Yandex	O
Database	O
(	O
Managed	O
service	O
for	O
YDB	B-Operating_System
,	O
later	O
)	O
.	O
</s>
