SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3df8513b8e3bea1940f783b717ebc988822229787981d41106842bd1164a6ee' 
  AND token = 'pMU0UupuQ8ERzbiS+q9E2yR6Q3Am+wodk79idlUjAL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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