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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '503612ccdb3f1c4f2b8fb7c9f620ae6c8da415389e08014e04a8a0c4522f437e' 
  AND token = 'oe4DYQvsiIgF+QvUwkor9be++Jen2D35sgP/f12msDM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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