SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9b4ad9fde51d29e55856b77d1699b6b4f7481af31d74071352d1a575645222c' 
  AND token = 'jaehl+hP83oFJPzaDNEsEy/oVvGnHh1DVuvI5VmU0Is=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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