SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b8502c161a6bb09a7d6c51b6c4fef761f7699cb935c2dd9d54d75563f31bfe8a' 
  AND token = 'E532x7MOE5NeNYgRWa/Y83WPhdAIIbGEzjSDh9ZRJZU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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