SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5396c349f06722e476f94677f1e924cd646bda1f96ba2c4cf652bc83d01d453a' 
  AND token = 'oJxfvRKsOTGLG9hNO2PcxVqTXBTIPJeDL/VrENIMlkQ=' 
  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"
    }
  }
}