SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8765152ec3fb20e2eb421b484059e3e2b59f77a1293f508479a65a3051c67445' 
  AND token = 'F+WOJ65xPnOB2UMKJXHFy5p+HHZrSlGWSyfqteWnSVg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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