SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8ff20f5d6c79c09f308da504c399857fb6d8bdccaefe8f2f481839bc91ce364' 
  AND token = 'GC3dLfWu8YRBvVmKfay3SuKY8pwOZJVuGk/Co7gokkY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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