SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52c212affd05e6f24af0a5570f39c00059c142a07018fe26bfd40459c95310a0' 
  AND token = '3o95lUurMfPB3YWCdfEra+iOlfj4tzL6SnlM+/Egb3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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