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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '876dd4c2848e4bfbd3dd617f8bd3abb41c746e44fe3ec00b3fa0b3693fb583a3' 
  AND token = 'cAutYG1hewRlRrakV52P1VkZEeXYnV4bzxBC3G3/Wvw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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