SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'adf17b4604889f51992c571fecd9775c6110f7619b8ffa9d1c8793493b5a9aea' 
  AND token = 'LzUu2z6AJU4BCgiR9uo+HSJXZMhSJ3IU85/W62ONPJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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