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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2c6921f25807cb31d0d744d7f9438a9d17738f2829effbb34c4ead3fcf1c71d' 
  AND token = 'Ss4TdpTRPcd3XCGO7G4PWK9Paaj2BTPAtnv9V+4PQTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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