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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'df2fe3f15d5c4686b256f061460335879c75fce3e810f6be4020ed5f9ba9df92' 
  AND token = 'g5j077dSUaSdRm2X3ySrS9d2zaZ1cdvRvlqizhkgS10=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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