SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '971098a20c05864262892a95d5846fbb23978c86930d31150c4ccb3aa280f2b9' 
  AND token = 'pUsdIZFGEUbgxDij+RPKBbDJ6+MQDe6Xvt7JgTPNCRw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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