SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aa743b8527ed2d2e733129b710683a017f36a1548595c73e1451e849383fa61f' 
  AND token = '348/ywBVxYCZya1ZctsuP4DIw+zELgruLUbAZOEUQGQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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