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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f261541e863c66380d0fb29ccdbdaec3cd276d8ab6497aed9834266d3c01b9b5' 
  AND token = '81+oiCGUSmf1fxD6ObIA3+rxqNxhmxBKKsFF6dgDkMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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