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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6dd342f84b2e5b2a83c450d1f9e5b96136e5504f7b62a32ec7eb4230bf2b588' 
  AND token = 'RhKpf3XJuOWk+ArPd/C2r4CeG19TIxh+k0dk5BjWaug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}