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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '89b0c2f3c61113eb38ede13e8dea7b419e65a34c132ceb26dc590818d88edc52' 
  AND token = 'MU+1XDcNHfipjbeqtSqT1dCmsAU4bYS9Wd0OIepN+R0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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