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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6f8359f62241b60412868d2e244082bf1e5cd8794d8a3a662fcfc1bf7b6cf256' 
  AND token = 'mU0AjYK9bf77nNnH2bnqFPQrHPtYrDVv2fIYcgPLD9c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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