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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6a96d1a39739aade59a687f99b372eeeff4ffbc9bd02f09b9e553546678a1320' 
  AND token = '6L7UBfJveNdIZUZbs346b5ViUHo0fD1rulgh1J1jrKE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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