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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b5f267b4cac22dc847be533d8102d15da6259ed34cd9d2cdf2b24a47a76cddfb' 
  AND token = 'eua+D6iwphCoQCn6KjJjBlxPerU8ReNvm804dh42ocE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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