SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76db9c777013558b583b2fdd8d9b1012c3f5fbef23cf338fce6abe834de48caa' 
  AND token = 'jbanaTTZ/hU4iYvGd/AJB1cobhdSSXtvkenIjQZZZvE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}