SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e0efd8c5a31548879ba4f8582e7344a327d7829bbf218dffda2fd276bc87e1' 
  AND token = '0P607Kkg73jo3pN3FTv3KwHoo+dNKh2UtdEKCeD4n9o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}