SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '37546bed533d62c89c7834d95f02a2b03a54af7b066d06f431777f05546be309' 
  AND token = 'KPqHIOAg2k0sD7UhmZfTjSrKAYllbVtQDsET/t2cAkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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