SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b077129726799120a5679a431e7c14b2e264aa4869a3af8f9fa331f9f06454c8' 
  AND token = '15TLTOJx2jyqysdmGdfQUPjBEshuMESHbOwznGYm3OI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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