SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fea1794f639ae1fc5ef231275ef9efaf6062e220391e9f111ac81396babc166' 
  AND token = '5IdphJN9x7wTgxktp2kUWPs0lPCyOsxrs2jTKTkaCts=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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