SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c59fca4fe88ddc9a81e022af222623338a8247136d0c613bcf4c1065bc8dcb96' 
  AND token = 'QixtKcWec+Z7Im/XsHAjhijcdr6sox6VjiysZSwuMRU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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