SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe8bea576a71d9af587562808ff51715b93b3fdd00da67f6754881bb2a6ea10f' 
  AND token = 'vxWcTFV7a0WffzZ4ZSkO5oPSuH0lIsk3NVXJ3MXsAKM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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