SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b374328479515a41c2f346e7e28f7ca3e47dbec804271165c8f7b35b4039e284' 
  AND token = 'Vk1preqdYoi0v0OaFId0P/tqLU52eYKZOH317vQgOi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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