SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6237e2f24ba5f3e91991b03b1bdf4dc0596a0d098a985a6c802db972b643225c' 
  AND token = 'qAmGWYkZzkB2Z2yhJwYjf9Tlf+fvD+Gb1p84uz3B2+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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