SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c6db3f3629a009059a53de02d79aa4d50ade39ffb2f1b90fc3d7b3f2dfdf6d8' 
  AND token = 'LKwdSPFomznGDO15jJiZgU1pgvWp+M/ZMTeo7SV+zfs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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