SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc638dcc039ae14aca812e5f576b04f96dbf01f4e0690e232a997f8a19d7791a' 
  AND token = 'C75B5KkInQuW0buCNAW/G9+GUqwDO53HE2pHZT/ULjs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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