SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6290d5e9f04edc9e5091228ff83006d85651cabbece5e5705bbe5bb43cd10947' 
  AND token = 'rhFlYDw3FV8lgnBnfZYyNPEltsAmr4CJiPJ64NlQp/0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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