SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8d0765240312114b8d972df0b99cf625594b5931a94010f2071a0d9d8800b0f' 
  AND token = 'oimUapDdZmkv15quTv6xEpiEH4I/ZSJG0tZJ4QZukcE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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