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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '17fc5ba6396cf64e1879c32b9484977b71bcde2cf69d06fb05e9d61fd5568f18' 
  AND token = '4Id2NmV2HMZ1GiHQTiFkHuvF+5ef1iBfRSMSshQJ0C4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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