SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '59b547cef2f4128777262829b3f90be49c865d2427c8f5da1c72c47a8abc094f' 
  AND token = '3+BYHqO++eg44QgT//j52NbxSUkq6qMGims31mLc/7U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}