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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '642bf24dfad8d4cf65313099e1c9b3e04bd7cdb5d1a60cbb185e26a16b1bdec3' 
  AND token = '6RFUu+ccJ0LAWBaw/RsB8bAxIkNc4KbfeI+zUta+0hA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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