SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '108f85568c8d16c798b911cac83920816bf09689d4b1a47038db90e6a22473e7' 
  AND token = 'atU3hopr1S3i7qvNdgbokacoLh4la6WGkiHOPochYcU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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