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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '75f1ef643c7d6ae29f3e6b2eb1fafe2cfd520f123e633f066e412ec3c75d8c9b' 
  AND token = 'a/VMioahDULi6+D/sZP31NcgbS0qJkesdH68nDJ0tZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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