SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b323b9ab8afdf3b23193f8b17179bf48c3cb572dde534d3eabec14e5bf9145c7' 
  AND token = 'oo3WHI44AANUa3HTBENgthUiNEVIdasvUHyoh6U1nKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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