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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c7f7ffb4f206c015bdef33c19dc0ec2dbe71872ffd054caa386b66d457667435' 
  AND token = 'vEehabQ+TAP1Z9QrdP2kx0AVJRBX3cbEvWPVtpisYTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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