SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4bc68714b94cf9a17167b6431684e768ee96637342c53f335eb509e940db1501' 
  AND token = 'fmuwsNGLTwfRTqMuTfn08x5fjtcRvW06TAhPogW4+Bk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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