SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18f2c0797ba08717927c8032226f2113cfb66d2515b1fb97aaeb8e6ee17a97c4' 
  AND token = '2kDb8jwFu9X2Vkk66YgZ7fRsvb1Xxv2I1QItcFY5z94=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}