SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3478441898efed9919fcf8a0d25eddb901bde98439eb16c20ef1ae4f189854a' 
  AND token = 'SK8slUh3AHtBG9M1L5wvyu2WuydfLSr6T1TO8cghLow=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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