SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e798057556185a42d3e9b7953c4ca3a1fb8944f12a524714c4fd3b7184006ff5' 
  AND token = 'frEcY3GtVkZ2X6BbShBfSAFLY2ZAHmhUjtgKE7pjhOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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