SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c03a670b39a4512f37f6b97deff9564117dd87dada6861d5fd03055eabf1ad6' 
  AND token = '+EMMvRA4gBW+LquYhs2tvFOmJrqVY3CjqDnJAuUp8Y8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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