SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a708e77b08014336c5e387fe50c1d4a9f73280185211b9a2745fc616b16035d1' 
  AND token = 'lTL/uXyhSauTU98LHfRC85OpruXRXiaSshpR6QaheRE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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