SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c31f903b7f2cec135b2837b6c3883182982f18daa9199a4cbc495f6675738f1' 
  AND token = 'PXU+vSnz6lAeNABZ2WLUT84XxRSN65wXhGrSqPCQzls=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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