SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb74de891e90606e54630fa203477076934791f92d8f88c57d8b945e41a62d6d' 
  AND token = 't2gjQyuQNYxzYgDaLXP8qswahFz55rPcvOkEbSAuNI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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