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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '21e80923441c7290930a112aa810a53e17e0d232013dab22a0c91a239df67f22' 
  AND token = 'Ss2d1J1jjMPtXtPushBejLllALTJOEhfTqxIbP4KSY8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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