14. A non-transitory computer-readable storage medium storing computer-readable instructions, the instructions comprising: instructions for receiving, from a client in a computer system, a query for retrieving a value of a key associated with an entity, the query including (i) an entity ID of the entity (ii) a key ID of the key; instructions for searching, at a server in the computer system in response to the query, a first in-memory object having multiple entity-key association strings to obtain an entity-key association string that identifies an entity-key association of the entity and the key, the entity-key association string created by concatenating the entity ID of the entity with the key ID of the key; instructions for obtaining the entity-key association string from the first in-memory object; instructions for obtaining an association value ID of the entity-key association corresponding to the entity-key association string from a second in-memory object, the obtaining further including obtaining the value of the key from a storage location using the association value ID; and instructions for sending the value of the key to the client.
14. A non-transitory computer-readable storage medium storing computer-readable instructions, the instructions comprising: instructions for receiving, from a client in a computer system, a query for retrieving a value of a key associated with an entity, the query including (i) an entity ID of the entity (ii) a key ID of the key; instructions for searching, at a server in the computer system in response to the query, a first in-memory object having multiple entity-key association strings to obtain an entity-key association string that identifies an entity-key association of the entity and the key, the entity-key association string created by concatenating the entity ID of the entity with the key ID of the key; instructions for obtaining the entity-key association string from the first in-memory object; instructions for obtaining an association value ID of the entity-key association corresponding to the entity-key association string from a second in-memory object, the obtaining further including obtaining the value of the key from a storage location using the association value ID; and instructions for sending the value of the key to the client. 17. The computer-readable storage medium of claim 14 , wherein the instructions for searching the first in-memory object to obtain the entity-key association string includes instructions for: adding a first string delimiter between the entity ID and the key ID in the entity-key association string.