SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab9726306b5883a9318e1186fee094070160a34297b9350496e505d8bae27a14' 
  AND token = 'fXUC7LMwnAzPNCPDOiYa0jn0JGXwlbRiC5feTnR9BPI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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