SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e71c2cf3e2c10b690db9df5fbb8879385b07b692d2478c85530fc31f9d88b2' 
  AND token = 'pZOCeWL70OMyMtottvCQR55UEASffZSMlmcPclcc8+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}