SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4cc03770bc50e47e646e8fc9894ce0d60bc1f451f9209c2a7b3e724c0cea938' 
  AND token = 'DDeTO2/iYph9AxIlbnxM8fp1+YIKWnQ9zWJEceKwmRA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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