SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a750bda6928631f2f237f6a96f9243cd03ea0d65ea822d408760ca357c482b1' 
  AND token = 'LSy61i0+wYeHxtvk4g6zHHx+K1Lh3/Mo997JIA8YzEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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