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SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'a6e78c2e8779b64fbaa8ad55fb91d3aa7be36dee1964a9daadb24be7b5791258' 
  AND token = 'xrTHy/9UYYQ/QDr7ycoZBHBzVxDbe23K0QW6KfnvkQ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}