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SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '21a435b8809c5aa67600b794302254b6353bc51438d897bbf7dc053d14069d13' 
  AND token = 'x/ycsDk2+KJ3leTLpyYwiuOopldEjpj39CYOR+srD+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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