SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdf5af951564b113525f3fe7731f32740f49b696bdb0990d57363e0fa44f8d3c' 
  AND token = 'csKN8bABPXfIlV5hhK58aNprgxDdjIVnWd8P2NPaq1M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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