SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc84b3ef764a9cf858a75bfa2210fa74ba21daaea2d37b1b103955458997a13f' 
  AND token = '6mnPe+JWokcZ/Cmz5v6iuJGyrHZSHBXGiNy4lXUBHKE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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