SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '07e3f948d20150761a6a96684420857139704426fab36079d934461d27108608' 
  AND token = 'cmdfQ0zAnHvgijdYMVG3eSl4NgrUjtmGBwxlZJ0xDqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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