SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2012848405c5f353112bec24804bf6c3a6769ea7bc8d729222ed2bbb2fd7456' 
  AND token = 'TJj1rsuBTXry56wfLIpUDs57yt0YzHkblSASaxazwwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00078

JSON explain

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