SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5e9921acd1df12633a6bf2cc1e7b7644942450c6e79e4a31bbdad8d3d832054d' 
  AND token = '7WiTJFMNE2fH6T3vhWmbtL7aFql4EoaKiWeYV/Ss4mc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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