SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b99283dc7873d1a743ee91a688dad78808ca914ddc0391cb478da5d9616ca7cc' 
  AND token = 'ZEroSV6WgTj2AGZ0VEx1AUTlirdy4fNyLRw742p/VFA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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