SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b12bd5bc56644fa28a9aa3822e934dd21a504e47408defc9be60a9beb686c21' 
  AND token = 'ECrbC5xF3+uKMw/JgJibuhqmmJy0Bho+5RJnKCWzenA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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