SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b7708a323a161299130a221421bd15ad9ba6eb56396aebfb7a6c45442bc26fc' 
  AND token = 'rWHEDhlEC6cuvafvpb4bTjQxxPVsu7uIc6hAUrdBbLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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