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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec2d334a5a1979c708402b4f70a3db8ed7efbe273bcd1d7d404c984d491cca53' 
  AND token = '5wEfzB4ay33YfRE+gdZZn8pFzPwK6bhgd4WhrnONvDU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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