SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8cb6abf78e521fca47367ffce1a51493d29e7ea04293987b49e6108913cef25' 
  AND token = 'KKxJ+DW+J6ROOmINBS9xtafwABrl5xEbBHEuBGJTocw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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