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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c251ed2d9b1cf071e3b59712cb7410b2326fe04dea10fd2cba84cf76dec3abde' 
  AND token = 'k0rhcUlWTLY+MkAuCORqJExJjUBBOUtnEP6S+HDr8oM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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