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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a821a78720d4144673d14e4aeedc9e1c295748af6ace56d5c09f7af8f8a0f260' 
  AND token = 'r6fvnNvbFVEId9kCdIeeV9RDr5V6ItTddY96t3XWtOw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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