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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '621aabad6e89934f5dcd84e756963d7b678c03eeebeef5add0e23a26c258eb35' 
  AND token = 'b28Ei5dsd7L9gv+u7rV/aa/+VFZ3NgmEHqryjhBkUJc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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