SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a35f58c246b315442dd8ee114a2152c68f3e75a6f7d83592e7c42a546085baf5' 
  AND token = 'XKFjChDdf9NCI+sveUaK0sciJCXcelVQcjEg3gMw8ms=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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