SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9757af63d8e4e5d36bb645f7b1e89d9f835aab91b6bbe7662976c8a25fae1a80' 
  AND token = '1id5sV/PKBqT6RW74umCx+wObpnEuHvDdVQRdbWN/zg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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