SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c51114ff8c5e106f67998688fff03d5835e0763dbdb768fe116bb2023c67d0ad' 
  AND token = '6TJH4wLSVJxXB9xa4l7DfTa9vIoKnyDQb+VuChFkKBE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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