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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6a4dcf33ea71f5eded0db495300af34284852600b40387d502e06697464d91c3' 
  AND token = 'gy7gKsq6llzv8pK6weWDWzz+2DIbgxSBAFmMQps8s3k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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