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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ab39b2a613b20c01567c02755feb5376980f89f2507c44f6aa55cad27bf5d74d' 
  AND token = '24wc0DeCLW7uKeANlWzRrBgtpJoZO1NwvyN7jeeM9YI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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