SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c403cbcf807510ffe652c41b2150edaae42a8875553060b48482e262d015101b' 
  AND token = 'a7T+owbAlJvSRZQqqms8QXqkKeBB71C/d1joA161pCY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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