SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68f2a6b9b27e88a3f0e1a5f4674a471ddf842b8157cdd2c34f9c136a93f7aa0a' 
  AND token = 'p+GYj6jzm8vMOoUTzWp1M6aL2/JYCSFqR08ChAunw94=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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