SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df8b1b21a43be4bfefdcbc938b63945001b49564f6193dceb396f8553d5b8ed0' 
  AND token = 'EGlDGPf723G0yJ5WrfpZlcCsJMWDYfEi4yPsKuxJ1wE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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