SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c72763828189748342120a67274819e0ebbe1b7e6e7167fecb550994b29a9c50' 
  AND token = 'dLshDXbhFhl5a0EE3rdMgG3mRCue9lbVGn1zMzaLaRY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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