SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a20b1dc1798f570d16c694fb075551e48549f1da2e2680a25ad94c262311fd5' 
  AND token = 'Rk0Z4nSgfnhqsdYt2BbCQqUru4XJjP59Z9IXJUKkUGc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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