SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b34ea82c20be397b8aebfb22971dd009b378b2352e25d8e75e5886b462d003dd' 
  AND token = 'kl/sSfhvwMaNPnw1JnLTkR0Tw/353bJoq+jczbsHpNo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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