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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3e86d9b9199942a0245084715edb2db33b6ecd3e4897df7d5eb69411a6fb268' 
  AND token = '6llbbGXLcOJGKqtXVxv5jWld+uAN7PSns4C8IfHXtOg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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