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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '75847f843c8b279a47c1e3301af529a1056d6d3c00fdcb1e6e52a1060b87a38f' 
  AND token = 'Zh7AyZLYLrfNgjG9T3WeGM42ocV0yWKUUu0wbvEOao0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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