SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3406fa0619ea12d73e454a2694cba9e39cf86f700bb9e00b3e844d8397a9b302' 
  AND token = '5gXU6xMwkEpZGQQ5hWMz4Pq/85CFZcVtlPyAmSBJM1I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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