SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9dbf3216774dcfb2248e2df6ec67c78f64aa3afa652575634fd52ee513c60d28' 
  AND token = '9i5yWQjesSNNXFVre9fvzm8SFxDeMobkGkvYDFFj/Do=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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