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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21a3a0b4b189344b4d1ad28c73eebce87aa06d2d706959c87af7753d94da1a57' 
  AND token = 'ht5oRAf0ITyx73NcjUXFVSqQf2N3hBE5NIlHoE7qDbo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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