SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c5a9e7b337a9d9031d363d86560241ec577baf498f1ca4e0a96e949a8d5281e7' 
  AND token = 'KSxKBL0M6yfsEAaWEKAjbn6rE9lzZn4JYRFSjQqv/BM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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