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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a81c4fd1dfa9aefc836354e541b540335ab0b0afb99beee149f9bce7c4dcfb' 
  AND token = 'prIuKGLQ/k/NwOTIKoNt1slK3+Fy3YqU958GxD8xgLk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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