SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '139710489ec502059d54ae6bb063fd2668f1f6c65d8fe2a29d90b778d3e1006b' 
  AND token = '1AMUrBRZRuouNG1ZzHJjv35+yKEG/8dU4IC/ibh1EAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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