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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6991ca0fac07f4dccc3c5da4172aeed6576527c040eb3a484999af4b0eb9c39' 
  AND token = '8p7h05tHZkIWmlBJdxvP5IbHTX+TD88qvtCsm4Tkh30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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