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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c558ae12ca1a072b75b678cd7b4088a9fa71f14f902b0dd0d5cd9c545f78e862' 
  AND token = 'tStsiPhE+QYm1Tb9TTPcDJbNbJd8nmXg6y8LXCzjwFg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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