SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '996e70df5f86974b07233adf8f933c2608a1ab19fada38623a7e62362d139b87' 
  AND token = 'lbI8q0/zmwqoCMB9Q0ODULk5n5Ha7EDcCKxFXDGoKxM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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