SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '729936cae85a210998436e2c71f171c79a75e4f4c0c236e8d793ff1792d2f3bf' 
  AND token = 'eXJqQuaxbiLYj0sVfkkdS4mXK+vRAb/zIKhfsWozkn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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