SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '381702410a56d71a17f222235356b91eaa3087514aa1504841170f13d8e92b33' 
  AND token = 'tXkI53jKCiUz8DEsAR4F2GOYENT1VvD1tznO4PPUCEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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