SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '998366d8b1af4f2a78b062fa303da01a12537e6859db0727308e851098eecc6c' 
  AND token = '3k/UMJIn2n/cBDzIt7RMKPRmLpI2kpLI/yOrNAySlBo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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