SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29baf3c16a6409b606d978be52c6861b011e9aaa0de983068b3e28f7e0c9934c' 
  AND token = 'PxgY39VFOpMTgRlxzUb9XUL6VC/TqagERzze+MglvjU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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