SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3e7d6ff53c96e116c2d03d934a9043657158210d04ee97b5962a24c77c9e0f84' 
  AND token = 'Isgh9pBs2Sw3NSgf+ZPh1KB2LnoPMM5VJsNGeDIk2cM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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