SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7b4f36062a2456699c53a02f5b65e37c6b5b8121d348d9661803182ef7d41f2' 
  AND token = '6s+rKTSLsDRuoxyM9ZQhIvLIobp9GugNmRuCTryG/O4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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