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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2756a88ff2174946ec40c67956dceabe82a6721e04db60a15d047ff50c5293ae' 
  AND token = 'arhIIZKishe5p1gRZdCY2kgBA5hfE5cbC4PalIABdRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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