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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5ac4b6b5d9e5c4bb4c7e38e50721c9843398e411a1cade230d97618dc193e04a' 
  AND token = 'ReZBVAc6NMDtEo55p+IUgUGZCM+wlk/RtVyVgaMIEG0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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