SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6eea6a0538d040c6d55726017f007e7cc75a0739fdac0ab4bbfa7c575f814830' 
  AND token = 'acsDem3YKtSC+G5PWT+labvhRP+VyL+YF0PabNahUnc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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