SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '74adfe726f51d5abab53a37bf6c18804e81fded3e71839955ead9a9436a4a18d' 
  AND token = 'DsMCVugOVa8MvSZ1nvaMxzcDNmuuXP5WUEY07AM5n2Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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