SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12f4ceddbbbe6f05f9be269ecc5339d03c9fc0f02575a60261ac6beea4650983' 
  AND token = '6oSk+2WRqyN0kwIhTUrarxNmUClI40Hlg9L2wGGReMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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