SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '261a203ff77c45a2fd36b755f0508548d76c571698fd929fa4dfcf6033d9f4b4' 
  AND token = 'qv/bGjfkCF/7MbWvR4SJ4z+Uzjwt08oW5rcH9FjE3sg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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