SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '307570a63dc307a35f05696e594499b8b151a2502d338dd901b66622ce0f5129' 
  AND token = 'VPggmYVy8JIzhde10fs9/5vQn+/PYNnXpglRP74PZ00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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