SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dec50d047b2509e1c07365f7a3b30c364f487b5afef86bc07ccf2cb0780ed1ac' 
  AND token = 'lDhAbwVUfiI3W+6TCEsK7IpqXdnQjPwGqJE8Ym0o5mE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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