SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '951518ba4d34883b21dbe89507779c499397b864dc12a6a9348917715ad40cda' 
  AND token = 'AY4HZKZVb2cRdSwvmQdEH75setaupaROFHsdncux3z0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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