SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '5c8200be8f2e50f2e6a95a6400b0c31ca86061a41ec15e936fd5b401b6536376' 
  AND token = '8qv+ib3zfbiG0a1iNCbOmj7mrH44Jo/pQZYKOjU1Tu4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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