SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ed6620ffbe953956d70f588e2837aedf14a43f981ec53df1fd4bc548500cff' 
  AND token = 'f2r8GyAgREMRV4KSpJT4pXsRers1Km1jLqCTZBI6xIg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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