SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2e18283f1b746eb0348da23873e16f91291b5205e74e75ddb93efa4fcc53978' 
  AND token = 'C9NRCVGYqZ+x07IML3u7+JUxonEKdXMtVBp55pgnW0s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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