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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c312f668944d62e5387824e621b6a339028bd07bcc4d2b31a8167534c1dc07ff' 
  AND token = 'QV6oqBDXzZ2VIUZyeSQamQ219wnZHRBuvf6Bl+DtbrU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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