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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cd8c88661fb3e74fb3a34a8d98ed5ee0d3b6116d1ad1825c0ed25bc0c30390e3' 
  AND token = 'UD6/2fa6Mp37tSRF0daVoqORED13XY9s/OzJU/3n3pU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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