SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83a251fb11811fdef130e54e0f7c509afe729c6aaaf5b6235bcaf28eca9393b4' 
  AND token = 'OTMTu13XFYE8SVfGI1zIjdYQpQE1UJWjMK6XYeoeNe0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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