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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c450934e05cc97a8bb5a94aeb8a1b1daf0ebb126e6d76abf5c08196b87a4f48c' 
  AND token = 'n7FdFFqYMcvey/M/WUn5UV2OT+yCc/fqPyWuCMEzGa0=' 
  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"
    }
  }
}