SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a6d4a63d4f00aec0422161760268c78bccea5b5001f9bf2d15c7c5c3a2c5926' 
  AND token = 'GQbXfJpvmQip2MKcHcI4GTaNUCGU4o4oD1ssBzCT+lY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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