SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c49acada3c50fbe6d496980c7d053288c792985d366390fd27088af506a0b379' 
  AND token = 'NiwI57h2AXTxyspHj2hJLZeK15VLKetph/bl/SBJmDU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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