ProfileService

ProfileService Example

I went ahead and copied the basic ProfileService example from their docs and I only edited 3 lines, it's that simple!

local Cosmoble = require(game:GetService("ServerScriptService").CosmobleServer)

and then I edited the Profiles cache and added the playerData variable.

Profiles[player] = {rawProfile = profile, Data = Cosmoble.new(player.UserId, profile.Data)} -- Create a cosmoble and set it to Data
local playerData = Profiles[player].Data

Final Result:

-- ProfileTemplate table is what empty profiles will default to.
-- Updating the template will not include missing template values
--   in existing player profiles!
local ProfileTemplate = {
    Cash = 0,
    Items = {},
    LogInTimes = 0,
}

----- Loaded Modules -----

local ProfileService = require(game.ServerScriptService.ProfileService)
local Cosmoble = require(game:GetService("ServerScriptService").CosmobleServer)

----- Private Variables -----

local Players = game:GetService("Players")

local ProfileStore = ProfileService.GetProfileStore(
    "PlayerData",
    ProfileTemplate
)

local Profiles = {} -- [player] = profile

----- Private Functions -----

local function GiveCash(profile, amount)
    -- If "Cash" was not defined in the ProfileTemplate at game launch,
    --   you will have to perform the following:
    if profile.Data.Cash == nil then
        profile.Data.Cash = 0
    end
    -- Increment the "Cash" value:
    profile.Data.Cash = profile.Data.Cash + amount
end

local function DoSomethingWithALoadedProfile(player, profile)
    profile.Data.LogInTimes = profile.Data.LogInTimes + 1
    print(player.Name .. " has logged in " .. tostring(profile.Data.LogInTimes)
        .. " time" .. ((profile.Data.LogInTimes > 1) and "s" or ""))
    GiveCash(profile, 100)
    print(player.Name .. " owns " .. tostring(profile.Data.Cash) .. " now!")
end

local function PlayerAdded(player)
    local profile = ProfileStore:LoadProfileAsync("Player_" .. player.UserId)
    if profile ~= nil then
        profile:AddUserId(player.UserId) -- GDPR compliance
        profile:Reconcile() -- Fill in missing variables from ProfileTemplate (optional)
        profile:ListenToRelease(function()
            Profiles[player] = nil
            -- The profile could've been loaded on another Roblox server:
            player:Kick()
        end)
        if player:IsDescendantOf(Players) == true then
            Profiles[player] = {rawProfile = profile, Data = Cosmoble.new(player.UserId, profile.Data)} -- Create a cosmoble and set it to Data
            local playerData = Profiles[player].Data
            -- A profile has been successfully loaded:
            DoSomethingWithALoadedProfile(player, playerData)
        else
            -- Player left before the profile loaded:
            profile:Release()
        end
    else
        -- The profile couldn't be loaded possibly due to other
        --   Roblox servers trying to load this profile at the same time:
        player:Kick() 
    end
end

----- Initialize -----

-- In case Players have joined the server earlier than this script ran:
for _, player in ipairs(Players:GetPlayers()) do
    task.spawn(PlayerAdded, player)
end

----- Connections -----

Players.PlayerAdded:Connect(PlayerAdded)

Players.PlayerRemoving:Connect(function(player)
    local profile = Profiles[player].rawProfile
    if profile ~= nil then
        profile:Release()
    end
end)