SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b8b3f977525723f2c6f99fd1acd49335a4bfebf4f9ebf4e1baecaa2f217813b' 
  AND token = 'mer9BRRInrK+WXPqwZsJwuSMYnGe6BAq1kGG/m39jXM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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