SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768b6137098966b903cb2e7e8eb634903a1493374e267ae254d10c3fcad9c2a9' 
  AND token = 'scTQZZfnqVKHyJfH2HiWtGGCRVKbwJBX2mngcfWRMVQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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