SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '500e83a979675d84c80ddd0bacae247bffc0e15c31189e5cb0f610f92f6daf36' 
  AND token = '1agkE7kuQYLNFA+7cRkNLSIZgRGhaXWLpwiQFyJvuGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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