SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1975d56cfeb4f224543b687b33b75a1d7dcbbc4407a5fc1555cfb5d286d739a2' 
  AND token = 'CGYEa+56RKnYZb9JiE/Kcpr0TBmbEfYgCsT9cCXp4Pw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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