SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40ceea2d4b86e795afc3d83f6febfcb97dbc0a5c3cb1f98bed5221164a79a481' 
  AND token = 'dJmhcspzm33NcL+fNsD/jBU/GXK33HoOxmbwkiR6YKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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