SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '80b786bc10fa857cb4ea39293b2c79e57f5ae5043440864d0f8f0cedd125f3c3' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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