SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '351509e790b998727c7c33a5a6254b0aad55f9bbbacb4d7f44e0f4ff52defe0e' 
  AND token = 'YNtuXriKU+bWsqlRGN0dJWGxKKfGD2NN8NqAF+oW0Qc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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