SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a575e57d8b10dac0fe51ff008b95f65a4e1a96d4ebadcac664355a5b38fc7878' 
  AND token = 'mJjJwoNez6SO8oLm+geQJT8EVnOzrcozV45kRMR/zWc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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