SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '59a9cafe2fd08f1cbd475da6e10cc4b671bc778bdb978371a97db10adcdee570' 
  AND token = 'YwvoNkwjW6+m27GWbE10+ZwDyI9HDcWgSOHnh6KpEm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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