SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '547845566be34a21c55f34068256d290dc66ed997c24d9f7399baadaaa06902a' 
  AND token = '9tL7t5tJVQAiQYkF5nGBBJbTAoGFN9lMF0grRDvf7gk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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