SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b076a5d41459801491959cb206ee54706cb7185648715b459cf1c14512621b4c' 
  AND token = '2DTWxdcyfg+BVrUSIF2tmP+4wIwVpUeRGucd77thMLE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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