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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7eb85c1720a050fb055f00d022a85235459f23ce57f4ef01d3908a3fed1b1e15' 
  AND token = 'JVwsrwN1iNjxaBmwtBTmp2Bwvgb1WiDJuiwa5ZTb7KI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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