SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90ba51bc0d68ba52a521f6fbc7d655732f290097e4efecfb6debaf2a10f69623' 
  AND token = '9HeX6LVuDzWukjBV2Pcaeel7pcIaulRhxigZUVvT6z0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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