SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5902ead4874d1aca6e7d3927e7e55bfe0bedc0a4332c70a78c6a9816b65deac' 
  AND token = 'upY5zaM7okAEwjADY4oOLGzUbrb7DJxFjDhyLVjPAsM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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