SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c81442a9ab9f7f690b835e6d24606a4dc2af222756da3b79057ca99149fb4fe9' 
  AND token = 'RGhJ/EQPE4NoiHIWiEqOGooQNZh5AH+LqFi3ntY2gjo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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