SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3251ce0589ebdc1d95c1057eeee4e2ada5c026d75a0cee2306457fe7827e9b8' 
  AND token = 'BKBsa8fma9Lr+bSTjXzU1yNHLCwi/feN1XwznqV2dzw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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