SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7990d01b5689c91c859b39e938c3fce301098a75e2a5f69043fb1fe2c5a2f789' 
  AND token = 'JjkpAosIgmw9XsGkiiTGYhMzHQeiL9xBb1gRrcxKL1w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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