SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c593bf993be11a5ed062e61492d28c0a1b2c51a2eb2fc2e5ec5ce4969dc0829c' 
  AND token = 'PgOajsa9JX9AWrFmpkp2qiOlFVXf6LfVUI8T6ARPnSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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