php - How to setup an efficient way to save volatile information to a database -

i working on web service following output (which partially works) result api request.

request

i built api accepts following request: post http://server.com/v1/requests/" parameters send on in message body.

response

status-code: 200 ok

{     "transaction_id": "12345",     "status": "processing" } 

table: requests

this creates new request on server in table called requests. table consists of fields (simplified):

transaction_id -> string status -> int 

i have table users in system

table: users

this table holds info users in system registered.

user_id -> string latlng -> float 

search users nearby request location

the algorithm have follow:

• when send request server, starting search nearest 3 users in range of request made. search being performed on users table , returns array of users near location searching (code not being displayed, works fine).
• this array of users sorted distance (nearest farest) know users close request position.
• i send push notification these 3 users asked if can respond request. can choose accept or decline. decision should saved database

when make request particular request, create following response:

response

{     "transaction_id": "12345",     "responders": [         {             "user_id": "r001",             "dispatch_time": "1234"         },         {             "user_id": "r002",             "dispatch_time": "1235"         },         {             "user_id": "r003",             "dispatch_time": "1236"         }], } 

this workflow clear me. totally unclear me how need implement table structure/algorithm efficient. questions are:

1. where store information 3 responders have been found database query? can think of ways @ moment: 1 adding additional fields in requests table each hold user_id. think of like:

|transaction_id|status|user_id_1|user_id_2|user_id_3|

|12345 |1 |u100 |u200 |u300|

i update same table entry each user responds request , @ end have 1 entry in table.

the other way thought of, be:

|transaction_id|status|user_id|

|12345 |1 |u100

|12345 |1 |u200

|12345 |1 |u300

this seems somehow strange me. don't blow whole table data @ end have 3x amount of data? how done in efficient way?

so right algorithm/structure receive output wishing for?