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SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '3762ff2d31a26c9a73e0bcf02dd0dc50af7f177c0e63b58c6296453935bb2c8b' 
  AND token = 'xvFSQcLdY+ltMEoLxyeyze6AKxBuWT7N3wLiaM/D2ac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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