SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '38fb0bd94bde9c932979c1f67396e61b543f97d884b427166daf1f63ad774cfd' 
  AND token = '3YSOJFq+x8MeQlPfOMANK2iYo/AIBtwPg56GRiAyegM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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