SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8fb0f141492ddc951c505c26f4b18fff12b52920a4d5ebd3c6095cda5642642' 
  AND token = 'EK+wUhHmeB7rFPm3GrRcyIguxfmdJBNousddHZ55YIg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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