<s>
Dynamo	B-Application
is	O
a	O
set	O
of	O
techniques	O
that	O
together	O
can	O
form	O
a	O
highly	O
available	O
key-value	O
structured	B-General_Concept
storage	I-General_Concept
system	O
or	O
a	O
distributed	O
data	O
store	O
.	O
</s>
<s>
It	O
has	O
properties	O
of	O
both	O
databases	O
and	O
distributed	B-Operating_System
hash	I-Operating_System
tables	I-Operating_System
(	O
DHTs	O
)	O
.	O
</s>
<s>
By	O
2007	O
,	O
it	O
was	O
used	O
in	O
Amazon	O
Web	O
Services	O
,	O
such	O
as	O
its	O
Simple	B-General_Concept
Storage	I-General_Concept
Service	I-General_Concept
(	O
S3	O
)	O
.	O
</s>
<s>
Amazon	B-Application
DynamoDB	I-Application
is	O
"	O
built	O
on	O
the	O
principles	O
of	O
Dynamo	B-Application
"	O
and	O
is	O
a	O
hosted	O
service	O
within	O
the	O
AWS	O
infrastructure	O
.	O
</s>
<s>
However	O
,	O
while	O
Dynamo	B-Application
is	O
based	O
on	O
leaderless	O
replication	O
,	O
DynamoDB	B-Application
uses	O
single-leader	O
replication	O
.	O
</s>
<s>
Incremental	O
scalability	O
:	O
Dynamo	B-Application
should	O
be	O
able	O
to	O
scale	O
out	O
one	O
storage	O
host	O
(	O
or	O
“	O
node	O
”	O
)	O
at	O
a	O
time	O
,	O
with	O
minimal	O
impact	O
on	O
both	O
operators	O
of	O
the	O
system	O
and	O
the	O
system	O
itself	O
.	O
</s>
<s>
Symmetry	O
:	O
Every	O
node	O
in	O
Dynamo	B-Application
should	O
have	O
the	O
same	O
set	O
of	O
responsibilities	O
as	O
its	O
peers	O
;	O
there	O
should	O
be	O
no	O
distinguished	O
node	O
or	O
nodes	O
that	O
take	O
special	O
roles	O
or	O
extra	O
set	O
of	O
responsibilities	O
.	O
</s>
<s>
Problem	O
Technique	O
Advantage	O
Dataset	O
partitioning	O
Consistent	B-Algorithm
Hashing	I-Algorithm
Incremental	O
,	O
possibly	O
linear	O
scalability	O
in	O
proportion	O
to	O
the	O
number	O
of	O
collaborating	O
nodes	O
.	O
</s>
<s>
Highly	O
available	O
writes	O
Vector	B-Operating_System
Clock	I-Operating_System
or	O
Dotted-Version-Vector	O
Sets	O
,	O
reconciliation	O
during	O
reads	O
Version	O
size	O
is	O
decoupled	O
from	O
update	O
rates	O
.	O
</s>
<s>
Recovering	O
from	O
permanent	O
failures	O
Anti-entropy	O
using	O
Merkle	B-Algorithm
tree	I-Algorithm
Can	O
be	O
used	O
to	O
identify	O
differences	O
between	O
replica	O
owners	O
and	O
synchronize	O
divergent	O
replicas	O
pro-actively	O
.	O
</s>
<s>
Membership	O
and	O
failure	O
detection	O
Gossip-based	B-Operating_System
membership	I-Operating_System
protocol	I-Operating_System
and	O
failure	O
detection	O
Avoids	O
having	O
a	O
centralized	O
registry	O
for	O
storing	O
membership	O
and	O
node	O
liveness	O
information	O
,	O
preserving	O
symmetry	O
.	O
</s>
<s>
Amazon	O
published	O
the	O
paper	O
on	O
Dynamo	B-Application
,	O
but	O
never	O
released	O
its	O
implementation	O
.	O
</s>
<s>
The	O
index	O
layer	O
of	O
Amazon	B-General_Concept
S3	I-General_Concept
implements	O
and	O
extends	O
many	O
core	O
features	O
of	O
Dynamo	B-Application
.	O
</s>
<s>
The	O
paper	O
also	O
inspired	O
many	O
other	O
NoSQL	B-General_Concept
database	O
implementations	O
,	O
such	O
as	O
Apache	B-Application
Cassandra	I-Application
,	O
Project	B-Application
Voldemort	I-Application
and	O
Riak	B-General_Concept
.	O
</s>
