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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a92bc87f03edcc6a909012b65f6b7be94386273d05c0844e45f9c70bdac6b339' 
  AND token = 'jFrG9Sbpe7N/PQj+vBRyW4FLA2w0Bu7DhCbp6ZvA8uQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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