SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e27ee15bca4db8693ee25070b595f33e55d557062009d0a9e649309c27063d84' 
  AND token = 'f3ATkFpsFwXtSmkDixZNYussHfZkvcdLCzFuY/3FMCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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