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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '728b87bf6345608f6ce5a2c2d3eb5ef53865e2d8448bd0b791e2239db27f3787' 
  AND token = 'Fd/LxcMN1iEYsr2pALTWfb5iuLZFFPNT1/KRmBoydlw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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