SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d804770fec3359e98ea84bff229c2b56549a1681b86342703ccfd9696ea2571' 
  AND token = 'BqPPvQAVlD7R47bol9ozFhZbNzIR0h33i++lJ7NhMWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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