SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28b6dff9715a5c1c0de7aacd324e9d3476f4ee03ae0f36d7799762cde232a382' 
  AND token = 'ebHQZsfqvMZXQwNGB0vgS+61pslY3EKIN+avodnxqJ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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