SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f9c915531513a2a34c96668354ae7f3f21b3321b140719468da1f53adc7d9c78' 
  AND token = '6zsR03C8oTgxK9ih1or1zsrn0BDJQrhAfYrwjPIKwfE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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