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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a7b848c747e710e0eb02921fa8fa49821e7492c6baf2e0ea575fa45e628e46a0' 
  AND token = 'RjmP8IRu8eWEjHb1lmTIkhyHvWH4Qs58bKDH7/ND+zQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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