SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91b24d43a2e97365058c55a0336325f3a66c84598e65807a1c7076e8583fb757' 
  AND token = 'Ll/pxU5SZDWdCgzdzluMHrPpmkSFC+roAxJLAKZXv/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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