SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '98ce2753b663258794f658e801588c859894e1ecd01a2f5da40c37598092470d' 
  AND token = '6EVjG5ckdC8RDS51FChGY+aITir5aUqUQ3RNmph9yv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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