SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9aaf117a90cb076d1a18c36279ae725d09b2cc6c204ec6176496a26467adc64' 
  AND token = 'E4rk1QdoNHiqMsPTBKtkp/AWokmAQsc5nWHzIBRsTUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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