SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfe54e0ffad928ff883a210dafa6048962b05d3225219129d94635f8405ad684' 
  AND token = 'GKeRB//M3iw+QxPbAtI2AB/AeWBhZaAJ6kdNAPOyuhs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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