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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5f3b2cb9943a93fdebe854f6afc34e8e94384ce894d8dbcc2d81af48bd436b4' 
  AND token = '1isgn2sUF4nTgo6WfUg8rXhMYQ7t1KV/FLdoJdZmqFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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